The first one is very true. The second one is not. You are something. 🙂
The third one? Hmmmmm... That's tough. Technically you can not do nothing, you're always breathing, your heart is always beating, your mind is always working. However, by social terms, you can definitely be doing nothing. Although I guess you did post this, so that's not nothing. Ugh! Grammarly keeps trying to correct "that's not nothing" and "Technically you can not do nothing" for me. I have to keep dismissing it!