I need to complete reinstallation process somehow and your suggestion is much appreciated, since you're dealing with commercial distribution for both FSDT and C9.
No, we don't deal in commercial distribution for C9 at all. We only programmed the Addon Manager that C9 uses for their commercial distribution, and for this, they pay us a license. This mean, we don't have any access to C9 customer's data.
Note that, for the server-assisted Reinstall procedure to work (I assume you want to use that one, because you might have forgot to create the .REG backup file), you don't need to have ANY access to your old e-mail! You only need to insert the Order N. and that email, but the program will reactivate in any case automatically: there's no need for you to check that email, because nothing will be sent there in any case.
However, this will work only if you have a copy of the original email receipt, so you know the Order N. If you don't, you need to ask Cloud9 to change the email address they have on the Esellerate servers for your orders, so you can receive the purchase receipt copy at the new address.
Note a difference between Cloud9 and FSDT Reinstallation method: with FSDT you have 3 different reinstall options: with a .REG backup file, with the server-assisted Reinstall or by directly inserting the Serial Number with the "Register Serial" option. Cloud9 products only have the first two methods so, if you forgot to create a .REG backup file and you already used the server-assisted Reinstall 3 times, you need to ask Cloud9 to reset also the server-asssited Reinstall counter (which doesn't have anything to do with reactivation or change of hardware)
Also, what would be your reccomendation for the installation sequence - C9 sceneries first and then FSDT products or an order is not important?
I'd start with everything related to Cloud9, and then FSDT. And be sure you have the latest version of all installers. Also, it might be probably easier if you install everything first, check that everything works in Trial mode, and then make all the reactivations.