US President Donald Trump's White House has earned a notorious reputation for its high-profile leaks, but special counsel Robert Mueller and his team have managed to remain remarkably tight-lipped about the sprawling Russia probe.

Key points: Michael Cohen and Michael Flynn are scheduled to be sentenced in coming weeks

Michael Cohen and Michael Flynn are scheduled to be sentenced in coming weeks The US president can be impeached for high crimes and misdemeanours

The US president can be impeached for high crimes and misdemeanours Robert Mueller's report will first be given to Acting Attorney-General Matt Whitaker

Mr Mueller's investigation into Russia's role in the 2016 presidential elections has resulted in indictments against dozens of individuals and three companies, as well as a handful of guilty pleas.

But the 18-month investigation — which has cast a long shadow over most of Mr Trump's presidency — is widely believed to be edging closer to its end game with a flurry of activity expected in coming weeks.

On Friday (US time), Mr Mueller is slated to release his sentencing memo for former campaign manager Paul Manafort after filing the heavily redacted memo for former national security adviser Michael Flynn earlier this week.

In the coming weeks, Cohen and Flynn are also scheduled for sentencing on December 12 and 18 respectively.

But does this mean the long-running investigation is finally wrapping up? And could Mr Trump actually be impeached?

Here we attempt to answer some of your questions.

When will Mueller release his report?

Robert Mueller's probe could shed light on alleged Kremlin meddling in the 2016 presidential elections. ( AP: Andrew Harnik )

No-one knows for sure.

In light of several recent developments, such as Cohen pleading guilty to lying to Congress last week, many observers have speculated that the probe is nearing its end.

Retired FBI special agent Frank Montoya Jr told the ABC the Cohen plea was indicative of how much the special counsel knows that nobody else does, and how far he had come with the investigation.

"I'll caveat saying that we're near the end by saying that if something else comes up, then they're going to take the time to look at it before they finalise things," Mr Montoya said.

"These cases usually actually take a while — this one has only been going on for about one-year-and-a-half and they've made great progress.

"The real challenge for them is not what they know but what they can prove."

Sorry, this video has expired Mr Cohen and his lawyer are confronted by journalists.

Another retired FBI special agent, Bobby Chacon, told the ABC the fact that Mr Trump had submitted written answers to Mr Mueller's questions was a sign the investigation was wrapping up.

Although Mr Mueller's team never said Mr Trump was the target of the investigation, Mr Chacon said it was also likely that he'd be the last person investigators would approach.

However, Samuel Buell of Duke University's School of Law added that it was "pure speculation" to say whether there was a report coming anytime soon.

He said recent developments suggested new information might be coming from witnesses, and that the special counsel also had prosecutions pending that could lead to further witnesses.

Similarly, according to a CBS News analysis of Flynn's sentencing memo on Wednesday, Mr Mueller's request for "part of an addendum to the sentencing memo to be sealed" to protect sensitive information linked to ongoing investigations suggests the probe may not be wrapping up soon.

John Q Barrett, professor of law at St John's University, said Mr Mueller's report could also be released in segments — as opposed to in one release — as areas of his probe are gradually completed.

Will the public get to see the report?

Michael Flynn provided so much information to the special counsel's Russia investigation that prosecutors say he should not do any prison time. ( Reuters: Carlos Barria )

While experts are divided on whether Mr Mueller's full report will be released to the public, they say it's likely that at least a summary will be made available.

But first, the report has to go through several hoops.

The regulations governing Mr Mueller's probe stipulate that he has to present his findings to his boss at the Department of Justice, who is currently Acting Attorney-General Matt Whitaker.

Since it's not a public report, Mr Whitaker isn't obliged to make it public and will also have some discretion as to what is relayed to Congress.

Mr Chacon said he had no doubt Mr Whitaker — if he was still Acting Attorney-General at that time — would also share it with the White House.

He added that it would be "unwise" for the White House to try to keep the report from Congress because the House of Representatives — which will be controlled by the Democrats from January — could issue a subpoena.

This may help to ease concerns that Mr Whitaker may try and bury the report after he once openly mused about a situation in which Mr Trump could fire Mr Sessions, and then appoint an acting attorney-general who could stifle the probe's funding.

Former FBI agent Montoya told the ABC that while Mr Whitaker had said "a lot of negative things" about the investigation before he took the job, the hope was that "he's a lawyer first and he recognises evidence when he sees it".

However, given the strong public interest in the investigation, Professor Barrett believed at least a summary would be designed for public release.

"There would certainly be a press and congressional clamour for the document, so I have trouble believing that nobody's ever going to learn anything about what Mueller reports."

What can we expect to see in the report?

Donald Trump with Paul Manafort at the Republican National Convention in July 2016. ( Reuters: Rick Wilking )

The much-anticipated report could provide the final puzzle pieces to unravel a so-far incomplete picture of alleged Russian meddling in the 2016 presidential elections, and the revelations have the potential to be greatly damaging for Mr Trump.

Since the start of the investigation in May 2017, the number of indictments, guilty pleas, and convictions have been mounting, painting a culture of endemic dishonesty in Mr Trump's orbit.

Mr Mueller was given sweeping powers to direct an FBI counterintelligence investigation examining whether Russia coordinated with Trump campaign associates to influence the elections on his behalf.

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The probe has also expanded to include Mr Trump's business interests in Russia, raising potential financing, tax, and money laundering questions.

Then there is Mr Trump's decision to fire ex-FBI director James Comey as well as reports he was considering ways to squash the Mueller probe — whether impulsive or considered — which injected a whole new layer of issues through potential obstruction of justice.

"[These things] are all still developing," Professor Barrett said, "I wouldn't hazard a guess about the likelihood of any of them producing devastatingly implicating information regarding the President.

"But they're all serious questions and obviously matters that Mueller is making good progress on."

Could Trump be impeached?

Donald Trump with Michael Cohen at a presidential campaign stop in September 2016. ( Reuters: Jonathan Ernst )

Yes is the short answer.

Under the US constitution, Professor Barrett said the President is impeachable by the House of Representatives for high crimes and misdemeanours — however it doesn't necessarily mean he would be convicted.

"Impeachment is a charging decision, and then in the event of an impeachment, the Senate has constitutional responsibility to have the trial," he said.

"So when President Clinton was impeached in 1998, that was the House charging him with two high crimes and misdemeanours, and then the senate had a trial at which he was not found guilty by a sufficient margin.

"You need two-thirds of the senators to convict."

However, it appears very unlikely Mr Trump will be prosecuted while he is still in office.

"That's a position that the Department of Justice has had officially for many decades — that a sitting president cannot be prosecuted," Professor Barrett said.

"But once someone is an ex-president, if criminal exposure still exists, that person could theoretically be prosecuted."

Is the investigation done and dusted after the report?

Virtually every investigatory committee in the House will pursue something from the Trump administration come January. ( Reuters: Jonathan Ernst )

Mr Chacon said the only loose ends to tie up are plea agreements and trials from the indictments stemming from the probes.

After the report's release, he said the investigations would be largely shut down and the office would be only funded to the extent that is needed to wrap the loose ends.

"But by and large there shouldn't be anything new coming out of the investigations [after the report's release]," he said.

"What they can do is refer anything that looks like it needs further investigation but doesn't fit into Mueller's mandate to other prosecutorial offices like the US attorney's office in the District of Columbia."