Hi Diego
Thanks for the interest. Let me try and answer those questions for you...
1. All my assets require at least 2017.3 but it works just fine in all versions of Unity after that. Basically, as long as you use .NET 4 (i.e. set Scripting Runtime Version to 4.x in Player Settings) then you are good to go.
2. Source code? Absolutely. I have never distributed a single DLL in all my life. Full source, always. :)
Check out the WordPress myCustom product for a free sample. It won't work unless you have the Login kit installed but at least you can see for yourself how the code is distributed. Unity code, Server code, Dashboard code... full source included for all of it. :)