A. You will have to pay penalty which is 50% of the amount you should have withdrawn but didn't.
You can withdraw money now, then file Form 5329, and attach a letter to explain why you missed the deadline, which is December 31 (if it's your first RMD, the deadline is April 1 of the following year).
The excuses could be illness, a death in the family, a mistake by your IRA custodian, or having an adviser who failed to explain RMD rules.