Sidestep is moving, not placing.

As I read it. as long as one of the 2x2's new squares is adjacent to one of its old squares, you can do it. So yes, you can effectively "move" a 2x2 2 squares.

And this is also why I have two G015 Magnetos!

Yes, technically they only officially covered 'moving' multi-base characters. Nothing about 'placing' them prohibits this. However, if we get a ruling, I wouldn't be surprised if they limit placing too the same conditions as moving.