How to update an firmware on RB600?
Where it to download?
What last?

Upgrade your RouterOS to v3.3 and then check in "/system routerboard" menu. It will show what you have, and the "upgrade" command will upgrade it to the newest one. It's included in RouterOS

What new at firmware 2.12?
Whether there is there a support new CF Flash?
When will be 2.13?

changelog is here:
http://www.routerboard.com/files/rb-2.12/CHANGELOG

no, new CF support can't be added by software.