Big day. Old door out, new in. Which included using disc cutter to open out doorway. Not without the cluster fuck of cutting through a electric wire buried around the door frame. Making good to come later. Triple glazed, old door wasn't even airtight!
It depends. Once you get one bit off the rest might basically fall off.
An SDS with chisel would be nicer but hammer will work. Start in a place you can't see easily incase you do damage getting the first bit open. Eye protection.
Yeah it's the edges, ugly as sin, like mine.