How to check if game in my inventory isn't demo/beta?

It usually says "Guest pass" or something like that on the item's description if it isn't a full game.

Edit: Just checked your inventory... you don't have any game in there so idk what you're talking about. Unless it's on another account.

Thanks for reply. I just realized there is description which says it contains two products: The Ship, The Ship Single Player, and when i click on their names it takes me to the shop page with full game, so i think it's ok to give it away (there is also nothing about demo/beta in gift's description).

The Ship has, on occasion, given away copies to people who own it, so that's probably how you ended up with a second copy. As far as I know, The Ship doesn't have a demo, so you're probably safe.