1: I want to rename the jid from 'test@xmpp.com' to 'phonenumebr@xmpp.com'
Right now nothing like that is implemented, as far as I know. If you use SQL storage, it wouldn't be much difficult for you to write some SQL code that traverses the corresponding database tables and replaces one JID with the other.
Of course, the contacts of those renamed accounts should logout and login to see the roster changes.
Relevant tables: users, last, rosterusers, rostergroups, spool, archive, archive_prefs, vcard, ...
2: Multiple jids associated to same account , ex('test@xmpp.com' and 'phonenumebr@xmpp.com')
Something like that is not implemented at all.