Doubts in CMT vs BMT beans

[Micheal John]

1. In CMT Stateful Session Bean, in ejbCreate(), why can't we call getRollbackOnly()/setRollbackOnly()?
Whereas, In BMT Staetful Session Bean, in ejbCreate() we can able to call getUserTransaction()? then why can't getRollbackOnly()/setRollbackOnly() can't be called from CMT Stateful Session Bean?

2. For accessing DB(resource manager)/other ejb reference, there should be either client / transaction should be in context. Am I right?

IN that case, for CMT Stateful Session bean, for afterCompletion() method is having access to clientinfo, but not access to resource manager and other EJB refereneces..why?

3. For exam, only CMT is there for all beans(Stateful,Stateless,Message Driven,Entity),not BMT is for exam?