delete my accepted Answer as it is not the right answer
I will answer your second question (so make a new one for the first).
If you have accepted an answer and no longer accept it because it is incorrect:
- Click the tick again to undo the acceptance. The answerer loses 15 rep, but that's okay.
If your answer has been accepted but it is not correct, here is the solution:
- If the system does not allow you to delete it, you can always leave a comment for the OP, edit your answer with a note, or flag your own answer. However, you should not have this problem because IIRC you can delete an answer that gets accepted.