How do i verify if a CD Key works?

Activate the code, obtain two tradable copies. Problem solved.

you can't. the only way, is to activate it (hence, lose the key)...

if it would be possible, many would generate keys and try them...

Give it to me i'll try it for you cough

You can test the key if you already have the game. It will say which game you tried to activate if it works. If its used, it will say invalid.

DO NOT FUCKING SPAM THOSE THING HERE

If its a The ship key, you will get 2 copies of the game in your inventory after activating it so just try it