The last update is much more stable, and this (if you look on the forum), is confirmed by many users, and fixed all the problems many users had with the previous version.
First question : Is it possible to re-launch Couatl ? (Couatl.exe doesn't reload Couatl into the simulator)
No, it's not. If with "reload" you mean it doesn't start on a 2nd sim session, check if it's still running from a previous run, with the Task Manager.
This can happen, for example, if your antivirus is blocking it or trying to check it, and it will also likely cause the crash in the first place.
Second Question : Is it possible to install an older version of GSX, with my last gsx-fsx-setup.exe ? or does it install the last version in all cases ?
No, it's not. If you saved an old installer, you can install that version if you install it with the network off. But it doesn't make any sense doing that, because you'll have other problems with sceneries, requiring the current version.
