I noticed one gets -25 points for deleting one's own answer. And if you undelete apparently you do not get those points back. Am I right?
No. You are wrong.
If you delete an answer the reputation change which occurred for that answer is annulled. That means the upvotes and downvotes on that (now deleted) answer no longer counts toward your reputation. (If you revive that question they start counting again.)
As a user you cannot delete an accepted answer.
There are no additional penalties for deleting an answer.