How much weight can this cat scratching post hold for a cat?

Supporting up to 22 pounds of feline activity.

Does this cat scratching post easily come off the wall when installed?

Use nano adhesive for a super strong bond, it won't come off / very stable!

Can this cat scratching post be attached to a sofa?

It's recommended to apply it to glass/ceramic tiles or wooden surfaces, so that there is no adhesive left when tearing it off. If you insist on applying it to a sofa, you'll need to purchase separate sofa-specific stickers!

Can it be applied on painted walls and wallpaper?

Not recommended. If removed improperly, it may damage the wall surface. It's best to apply it on glass, ceramic tiles, or wooden surfaces!