A diamond promise ring has many meanings, but they generally means that the giver of the promise ring will be faithful to the receiver of the promise ring.
He only had sex with here
Only he can answer your question: there is no standard.
it is a gift
It means to carry though and complete what you promised to complete. For example, if you paid back a loan, then you fulfilled your promise. If you promised to help someone with a project, and did follow through and helped that person, then you fulfilled that promise.
If you mean someone's PC, someone will eventually turn into the name BEBE'S PC Hope I helped :)
A Kappa Diamond is what is known as a frat "sweetheart." This generally refers to someone who isn't in the organization officially, but does support them.
A promise ring is given to women or girls before the actual engagement ring is given. It's a promise to marry and if the person who gives the ring chickens out, he can be held accountable in a court of law if you wanted to take it that far.
To do what you said you would do
A promise ring can mean it is a promise that one day you will receive an engagement ring, but, things could have changed and it could be simply a promise ring of friendship forever and you need to have him clarify what he means by giving you that ring. If you do not love this young man and he has romantic intentions then do not accept the promise ring.
It could mean that you have pestered him or have had sex, so he gives a generic "some day" promise to you so you will leave him alone. This is not something you can bank on. Someone who is truly interested will have similar interests as you do and getting together for a date will be definite.
"A diamond in the rough", is an old saying meaning that with a little improvement(s), you could reach perfection.