(1) If my certificate was already expired and would like to use personal certificate from ASGCCA. How can I do?

Because user could not use the expired certificate access the rekey webpage, please go to here to execute the step 2 to generate the online CSR.

(2) How to get the same Distribute Name(DN) of the certificate if my certificate was expired?

If you registered to many services as member, and you don't want to register again. please go to here to execute the step 2 to generate the online CSR with Mozilla Firefox. CA manager will deal with your request as soon as possible.