Unlike its predecessor's circular components, this device has a square camera sensor and a rectangular power button. The photos of its interface below also indicate that it's loaded with Android Lollipop out of the box. According to Yonhap News, the G4 is supposed to have a curved, 5-inch Quad HD display -- we can't really see any curve in these images, but it might be due to the phone's angle. Of course, this could be a different phone altogether.

Update: Some eagle-eyed folk have spotted "M8936" in the baseband version, which would suggest this phone holds a Snapdragon 610 -- not really what you'd expect in a flagship (where an 8-series would be more appropriate). Unless this was an early prototype with different innards? Or maybe this is just some sort of variant of the G3 Stylus. Either way, we won't know for sure until LG officially unveils the new flagship phone by the end of April.

Update 2: The OP has shared another photo of this mysterious device, but this time with the stylus in its full glory.

[Image credit: s3rv1cet3ch @ XDA Developers]