It's usually used when you are surprised to learn something. Other uses are to add how serious you are being about something. The last and most obscure usage is to explain the status of a couple. They are "For Realsies" if they are officially dating.
The same as fo'real but was instead created by Crabstickz; from Youtube, in his last 'Advent Calundah' video before Christmas when almost falling over.
Similar to action of popping a wheelie, in the way that wheelies rule. A wheelie is pretty cool and so if you can do one, you are in fact pretty cool. So it is like an emphatic "for realsie", meaning you have done such a cool "for realsie" you are cool. Something that is a "for realsie" with a bit extra "real".
Dude: "Dude! My ex just tried to weasel back into my life!"