If you turn 17 tommorow can you still buy a M rated game TODAY?

depends on the type of retail store, online if you use paypal or a debit/credit card for minors you can lie about your age, in some retails stores they won't check or ask for an I.D. like in Target the cashier may just look at you and check for a mustache or so as large retail stores are too busy to check age unless its cigarettes or alcohol, at Gamestop no as they are strictly focused on games and they have a strict rated M game policy.

Sorry, you need to turn 17 in order to purchase M rated games. You also need to show them some kind of identification at the counter, so it wouldn't matter anyway.

No, you can't