How long can you test games with xbox game pass?

So the games are not mine if I download them with the gamepass but how long can you play them? One week a month? And if you want to continue playing you have to buy it

Are the games full version? What if I play through it then I have no reason to buy it anymore Or are the games offered until half the story

As long as you have the gamepass. - The first test is mine for 14 days free of charge.