Friends with benefits can do things couples can do except without being labled as a BOYFRIEND and a GIRLFRIEND, when you ask if they want to be friends with benefits with you, you both have to agree on what those BENEFITS are, and it doesn't have to contain sex. If you both agree on sex, then it's also considered as friends with benefits.
Guy: Want to be friends with benefits?
Girl: Sure, but what are the benefits?
Guy: Hugging, kissing, holding hands.
Girl: No sex?
Girl: Okay sure then.
Thats an example of becoming friends with benefits. You can choose the benefits you want! It doesn't mean you have to have sex or oral or anything, as long as you decide the benefits you want and you both agree on it, then its official.