Plain answers to what buyers ask before they buy: what NFA means, what Prime and Premier need, and what to check before paying.
NFA most often means non-family-shared: a standalone Steam account that is not linked to anyone else's library through Steam Families. In account shops it is also read as non-full-access: you receive a way to sign in, not the account's email. A KeyScope account is both: a standalone profile, delivered as a Steam ID and a login token.
Prime Status is the upgrade to Counter-Strike 2, which is otherwise free to play, bought in the game or on its Steam store page as a single package, not a subscription. Valve requires it for Premier, and only Prime players earn XP, service medals, skill groups, CS Ratings and weekly care packages. You can buy it yourself or buy an account that has it.
To play Premier in CS2 an account needs two things, according to Valve: Prime Status and Profile Level 10. Premier is the Active Duty pick and ban mode that ranks you with one CS Rating instead of per-map skill groups, established by winning ten matches. A Premier ready account has both requirements met and no rating placed yet.
Buying a CS2 account is against Steam's Subscriber Agreement, which does not allow accounts to be sold or transferred, so there is always a risk that the original owner recovers the account or that Valve restricts it. If you still buy, check what is delivered, how long the warranty lasts, and whether a failed account is replaced, refunded or credited.
Ready to compare the accounts themselves? The CS2 shelf lists every line with its live stock count and price.