I am not so sure about the AhlulBayt as mourning activity taken place and wondering to know, from ur reply to the question.
1- Beating the chest is it right?
2- Beating with something that cause a mark or blood is it permissible?
3- Open/ tear the shirt among all mahram is it ok?

Non of these things is directed by Ahlul Bayt. It is a common practice, that was introduced by people as sympathy.
However, although it is not part of the teachings, it is not haram in it self.