Some Questions.

1. How do I know what computer is connected to the local wifi and what OS are they using?
2. Is OSX/iOS hackable? How?
3. Is Window 8, 8.1 and 10 exploitable?
4. Is there an exploit that is compatible for most system?
5. EDIT: Also, my friend said that: LOIC and ping command in cmd (enter ip/website here) is a type of DoS and he tried to DoS google this morning, true or false?

Thank you guys, i'm really new to this, i'm sorry if i ask more questions :).