Age appropriate dating is the most important thing to emphasis here.
At 15 - "dates" would be going to school events together or maybe going to a movie on a Saturday AFTERNOON. No "date" should ever involve truly "alone" time. Group functions would be the appropriate setting. Unless a school function is involved, "dates" should end early. (So, date curfew would be home by 7 pm unless it is a school event that ends at a later time - then curfew is home within 30 minutes of the end of the school event - like a sports event or a school dance)
At 16 - "dates" would still include the items for age 15, but add a little more freedom on the "curfew" time. So, at 16, date curfew might be 9 pm.
At 17 - "dates" get a curfew bump to 10 pm and no longer limited to just school functions and group settings.
At 18 - The curfew bumps to 11 pm if they are still a high school student. If they graduated - no limits - they are adults.
As for how much physical contact happens at each age - parents can only discourage them from having sex. Once the teen is out of their sight, anything could happen even when trying to limit dating and limit the amount of time teens might end up along together. If teens really want to have sex - they will find some place to do it. Anything past kissing, hugging, and holding hands shouldn't happen until after 17. No teen should be involved in actual sex acts until 18 and older. But - honestly - you know most teens have at least done heavy petting by the age of 17.
Personally - I always thought it was more important to let my daughters know that I would prefer that they didn't have sex before the age of 18 but that if they ever thought they would, then I wanted them to know all their options for preventing pregnancy and STD's. I was never the kind of parent that just said "no sex." I always wanted them to know they could talk to me about anything and I wouldn't become angry. My two daughters both adults now and we never went through any pregnancy scares - and I do believe they would have told me.