Can you get an STD/STI if both partners never had any kind of sex before?

No. Stds are not created out of thin air, some one has to have an std in order to infect you with it. Or you have to have an std in order to pass it on.
I've you've never had sex before then you're not likely to have an std. The only thing that virgins could have is cold sores, which are commonly passed by being innocently kissed during child hood by some one that has them. If you happen to have cold sores avoid kissing on the mouth and giving oral sex while you have any signs or symptoms of a break out.

No you should be fine, however if it's gay penatrative anal sex, there is a chancec the top guy can get a urinary tract infection from feces from your rectum entering the uritha of his penis.

Either he uses condoms or you wash your rectum out with a bulb syringe an hour prior to sex.

Most people have herpes from kissing, so unless you do oral you should be fine

Yes, no scope.