in order to run a DownGrade from 7.7 to 7609, which are your suggestions?

We have a MS SQL supportcenter DB backup of  7609 rel.

We think that make a supportcenter backup ( 7,7 rel ), after unistall the pmm file with updatemanager and after  restore the DB of supportcenter at Rel. 7609.

But when I start the uninstall i have a error "uninstall not supported" !!!

Now ? 

What do you think about ? 

We need to uninstall All  and reinstall only 7609 rel ?

But after complete uninstall, the manage engine folder are not deleted. The manual delete cause windows error because one or more filename are too long into folder patch and other folder.

Please let me know if you have a solution for Downgrade to 7609 rel.

Thank You

Best Regards

Alberto