new QTP 11 installation

[adolf.koh]

I am new to this forum.
Hope to get some advice on my faced issues.

I am going to upgrade my QTP version from 9.5 to 11.

My questions:
1. Can QTP 11 modify and save the test script in version 9.5?
2. Can I maintain 2 version of QTP, Version 9.5 and Version 11 as different version are being used by different project and my user?
3. any impact to the QC if I upgrade my version from Version 9.5 to Version 11?

Thanks

Warmest regards,
Adolf