Tickets for overseas

Hey, first time going to summer sonic and I'm planning to buy tickets now but I'm not in Japan atm, some questions:

-When I buy tickets, do I claim them on my phone ? Or do I need to claim them somewhere irl in Japan ?
-If I buy 3 tickets, do 2 of my friends can use these tickets to get in with me ?
-Do the staff let you in at anytime ? So if I plan to go see an artist performing in the evening can I get in at 6 PM ?

Thanks in advance !