Beside this, can I put my motherboard in a different case?
Generally you can fit any motherboard who's form factor is smaller than the case you are using. Exceptions apply as with anything, cases made for the likes of Dell or HP may have fixed standoffs which can prevent installation of 3rd party boards.
Furthermore, can I move my PC into a new case? It's possible the new case already has one in place. If so, you may need to remove it to insert the one that matches the ports on your motherboard. Move the motherboard onto the risers, aligned with the screw holes.
Also Know, will an old motherboard fit in a new case?
So, long story short, every motherboard does fit in every case, if the case is big enough for the board, unless the motherboard or case uses a non-standard format (generally because a major pre-built brand would rather sell you a new computer than have you putting new parts into their case or reusing their board in
Is it hard to change a PC case?
It's not overly complicated. Depending on what components you have and what case you're moving them from and to. You unplug everything and move it to the new case. Say you have a standard build with mobo, cpu/cooler, gpu, ssd, hdd etc.