Regarding your first question, it's probably game-engine specific, but you should be able to do it.
Clipping is subject to limitations Clipping - Spine User Guide but I don't think that the fact that your receiving character has a clipping should prevent an animation from being imported.
As I wrote above, it's very important that the bones names across skeletons match. You might have more bones than the source skeleton, but not less. You could recreate the missing bones and then delete them after. Or you could make a copy of your source skeleton, delete the bones that are not present in the receiving skeleton, then try to import the animations.