I never had a problem disassembling, moving and reassembling even their cheapest pieces of furniture. I think their reputation for falling apart comes from trying to move them fully assembled.

Last week I had to move a 3 door kleppstad from one room to another, and I think I made a good decision to take off the doors to reduce the weight as much as possible without fully taking it apart. But if this piece of furniture needs to move any further then I'm fully disassembling it. I would rather not risk taking it down the stairs fully assembled.

I assume so, because I've done it (repeatedly) and there's never any glue involved. The Billy book cases used nails for the back board, but it's easy to get those out by tapping the board from the front.

It depends which items. They're not designed to be re-assembled but some pieces will re-assemble just fine. You have to be careful as it's easy to strip the screw holes e.g. in particleboard. I'd try to remove any shelves, doors, drawers, etc. and move the rest as one piece, giving it a quick tighten when you arrive.

i ve split and moved my bed at least 10 times. Everything else has been disassembled at least twice moving.

Most stuff can be disassembled once or twice.