1. Is it necessary to uninstall GSX from the old system to install it in the new one?
No.
But if you select the DEACTIVATE feature on the Addon Manager on the old system when is still working normally (before getting rid of it or reformatting it), you won't consume a new activation ( of the 6 you have available ) when reinstalling on the NEW system.
Once you Deactivate on the old system, GSX will revert to Trial mode there, and then it becomes irrelevant if you want to Uninstall it or leave it there, or reformat.
2. What are the procedures for uninstalling GSX? Also is there any manual for installing GSX in the new one? I would like to review the process of installation of GSX.
If with "uninstalling", you mean removing the installed product, it's made just like any other Windows program out there: from the "Add/Remove Programs" section of the Windows Control Panel.
If, instead, with "uninstalling", you mean removing your ACTIVATION on that system, it's done using the "DEACTIVATE" function of the Addon Manager, which is entirely unrelated to the act of Uninstalling.
And, this is not even required: it will just save you one activation, but not much will change if you forget to Deactivate, it's just the next installation on the new system will use another activation, of the 6 you have available.
3. What is the latest version number of GSX including all the vechicle and other updates as of today? Is the gsx setup on the home page of FSDT the latest version including all the updates?
ALL the installers found on our site at any given time, are always the very latest versions.
Since our Trial versions are 100% complete, we don't need to publish patches, considering our installers are not very large.
This means, you can spare you the trouble of keeping a backup of our installers, because they are always freely available here without any limitations on the download, and are always kept updated the very latest version so, whenever you need to reinstall something, it's easier to just redownload it and don't lose time wondering if you have or not the most current version.