How do I blocked launching the game on several platform ?

Hello, I would like to apologize in advance for the way I speak English, I use Google Translate to write.

So I am going to create a game and I would like to know how to avoid launching the game on several platform because I noticed that it was possible to launch the game several times and to progress much faster on my game .

I am able to do something with AJAX (side Construct 2) and PHP / SQL (listed website)

But I do not know how to do it?

If necessary, I use the "Firebase" plugin for the database.

Thank you in advance !

edit:

To simplify, I would like to avoid the user being connected several times with the same account. To know that I had thought to do something with the IP address but if the user runs the game several times on the same computer it will have no worries being given that the IP will be the same ..

I'm not familiar with Firebase so not sure how much I can help.

Local Storage is shared for games opened using the same browser which you could use to prevent some cases of accidentally connecting twice.

Maybe you could on starting the game set some random value that will be different each time and use it like IP.