Can I play games with one ID on Steam at the same time?

pu1. You can access Steam with one account at the same time, but you probably can't play games

2017-12-25

OK

pu2. You can play games in Steam offline mode

2017-12-25

OK

pu3. In the case of packages, I think it's possible if you cut off the Internet

2017-12-25

OK