I would like to Upgrade from Professional to Platinum on a monthly payment Schedule, as I have now for Professional. Is this possible to change plans like that With ease? Or do I need to reinstall Sonar, Addictive drums 2 and Melodyne for this, since I already got a Serial number for all these software. I already bought lots of packs for Addictive drums 2.
 
I Guess it will be 49,99 a month, since I have only paid for 3 months, but what about the 19,99 I already paid for Professional this month?
 
I Sent a email to support but maybe someone here knows if it will be like a separate full install or a Upgrade install. I do not want to loose all my AD2 packs if I will get a New Serial number over there.

You don't have to do anything as far as upgrading,, just pay the extra and they will let you download and install Platinum. I bought it outright on sale for $150. 
I still have Professional installed ,,, hard to tell a big differance really, just the new features which I've yet to use. 
I'm a few months behind on the updates so I've yet to encounter the new start screen. 
But you can have both Pro and Plat installed side by side. Not that there's any logical reason but myself I just havn't bothered to remove Pro.  I open both from time to time without even realizing which is which unless I look closer at the icon. 

Okei, thanks.
 
I will wait for the support to get back to me then, so I maybe can pay the extra this month and then move on with the platinum plan.