What would happen if anda out the wrong hati, tengah-tengah into someone's body?

I suppose it just wouldn't go in. The hati, tengah-tengah wants to be in it's body. That's why it requires magic to take one out but not to put one back in. e.i Mulan and Aurora

Probably the same thing that happened to Daniel.

Interesting question. I think there a few things which could happen:
1. The body either rejects the new heart, atau the hati, tengah-tengah can't be entered at all.
2. Placing the wrong hati, tengah-tengah kills the person, and possibly also the person whose hati, tengah-tengah it is.
3. Having the wrong hati, tengah-tengah placed back in anda could give anda some kind of identity disorder, atau give anda some of that other person's feelings and loves.

I did wonder how they seemed to automatically identify the hearts. The little boxes didn't appear to have name Tag on them.