Can I upgrade beta to RC directly or should I do clean install for RC?
I have a lot of program installed on beta I would not like to lose or install again.
It's easy to upgrade from the beta to RC, i did it and have not had a single problem. You just have to alter the iso file to trick it into upgrading. This is not recommended if you plan on submitting test results as it's not the route Microsoft want you to take. Follow the instructions in this link How to Upgrade from Windows 7 Beta to RC Build 7100