If I understand correctly I need a second key for level 2 which is not the one when I bought GSX in 2013
Of course. L2 is called "Expansion" for a reason, it came out in 2018, and it's a separate OPTIONAL purchase.
When I bought GSX I only needed the one key that came with the purchase and GSX worked fine.
You GSX key STILL works fine, but it will activate only the base GSX feature you bought back then.
Should you buy this level
It of course depends on you. Are you interested in replacement jetways world wide, animated passengers and a fuel hydrant service ? If yes, you need GSX L2.
or how to get it.
Our web store, there's a GSX L2 product on sale, which will get you a GSX L2 activation key if bought.