Any changes on a contract typically need to be signed or initialed by both parties. I believe it is legal for them to change whatever they want, but that's a "counteroffer" not a contract. Thus you'd need to sign away on those changes (indicating you accept them) before it became a "contract" between you and the seller. This is my understanding, but laws vary from state to state, I would consult a REALTOR licensed in your state and perhaps an attorney.
And regarding your first question, yes I believe those are all names for the same thing, but again I would ask a local REALTOR as they could differ in your market for all I know.
Broker, CRS, GRI, ePro
Raving Real Estate
Laramie, WY 82070