A reclusive, braces-wearing teen who lived behind a white picket fence with his devout Muslim family was secretly an ISIS sympathizer — and was plotting to launch a knife attack at a Dunkin’ Donuts and other targets near his Queens home, the feds alleged Friday.

His getaway vehicle of choice? A Razor scooter, federal prosecutors in Brooklyn say.

Awais Chudhary, 19, planned to strike at the Dunkin’ just blocks from his East Elmhurst home, and was also targeting pedestrian bridges over the Grand Central Parkway to the Flushing Bay Promenade and the World’s Fair Marina, prosecutors said in court papers.

Chudhary had texted back and forth with two undercover agents he believed were ISIS terrorists, sharing his attack plans and telling them that he’d pledged his allegiance to the terror organization, the feds said.

At one point, he allegedly sent one agent an ISIS diagram of the human body that he’d found online, showing where best to plunge a knife into a victim, the feds said.

He also allegedly asked for guidance on constructing a small “bucket bomb,” which he hoped to fling from an overpass onto vehicle traffic below.

“May Allah not turn our hearts away or make us ever doubt or hesitate,” he allegedly texted.

Chudhary was arrested in Queens on Thursday as he tried to pick up items he’d ordered online for his attacks: a tactical knife, a mask and a special wearable strap to hold a cellphone he’d hoped to use to livestream the carnage, the feds said.

The wiry, bearded teen was ordered held without bail at his Brooklyn federal court arraignment Friday on charges of providing material support to a terrorist organization.

“This is not something where he’s masterminding something in the subway or Times Square. He’s looking at a Dunkin Donuts,” his court-appointed lawyer, Samuel Jacobson, argued in asking that bail be set at $100,000.

The plot was just a “fantasy,” the lawyer insisted.

“In reality, he’s a kid. He’s standing here before your honor wearing braces,” Jacobson said, as the teen’s parents and a cousin listened from the audience.

“The most terrified person in this room right now is Mr. Chudhary,” the lawyer said.

“By all accounts he’s a kind, shy, caring young kid who’s living with his family.”

Braces or no, Magistrate Judge James Orenstein remained unconvinced. He noted that the age of an attacker can mean nothing, noting the deadly attacks by young people in Newtown, Conn., and Columbine, Colo. — and that Chudhary was planning to “kill his neighbors.”

“Was it a fantasy? I hope so,” the judge said. “But I can’t ignore what the proffered evidence makes clear and convincing.”

“The defendant is a danger to the community, and a significant one,” the judge said in denying any bail.

Chudhary’s shocked upstairs neighbors say they barely ever saw the timid-looking teen.

“I didn’t even know there was a boy” living with the family downstairs, neighbor Luis Bravo, 53, told The Post on Friday.

“I didn’t even know there was a guy living here … for two and a half years we’ve been living here. My daughter maybe has seen him a couple times.”

Bravo’s daughter, Xitlalli, 18, said the teen was very religious and wouldn’t even listen to popular music.

“I literally over two years have only seen him twice,” she said.

Then, at 8 p.m. Thursday, FBI agents banged on the front door shared by the Bravo and Chudhary families on quiet Butler Street in East Elmhurst.

Bravo was upstairs in his kitchen with his own son.

“We just heard a bang — three bangs at the front door — then they shouted, ‘Open the door! FBI!’ ” Bravo said.

“It was a big surprise for us,” he said.

“So then I hear a big screaming downstairs, like children. And I believe they broke into the apartment on the first floor,” home to the Chudhary family, he said.

Chudhary’s father works long days outside the home, and the mother always wears a niqab when she goes outside — a head-to-toe covering that only shows her eyes, Bravo said.

The couple have another teenager, a girl, and two little girls who appear to be in grade school, he said. The house is owned by a relative of Chudhary’s, he said.

“What happened?” Bravo said he asked the agents.

“They ask me, ‘You live here? Who else is here?’ Obviously I told them. I have nothing to worry about. They say, ‘We are in the middle of a situation. Don’t worry about it.’

“They ask us the regular questions. It was me my son, my wife. They ask, do we know the people downstairs. They told us they couldn’t tell us what’s going on but with the news, as the day passes, we’ll know. But they were searching everywhere in the downstairs apartment.”

Only later, when he went online, did Bravo learn the shocking charges.

“We read on the internet police had taken into custody a boy, 19-year-old, because he was planning to perpetrate a terrorist attack,” Bravo said.

“That surprised me. Because they are very quiet. They don’t talk to nobody. Maybe it because their religion or something. They carry out their own business.”

Bravo was still in shock Friday as his teenage neighbor stood for arraignment in Brooklyn federal court.

“A very quiet family. Very religious. They very rare talk to somebody else,” Bravo said.

No one in the house knew what the teen may have been up to, Bravo said.

“They were in shock,” he said of the Chudhary family. “The boy’s father was sad.”