Since I have 4 year degree and want to join the NG as an officer, do I have to enlist first? Can I apply for OCS in the NG or Reserves?

The recruiter just wants the enlistment credit.

You need to talk to an Officer Strength Manager (OSM), who will contract you as an OCS candidate.

Do NOT enlist first. You need to ensure on your contract is says “09S” i believe meaning you are going from BCT to OCS. Find a different recruiter who’s willing to help you if you have to.
I was talked out of going to OCS and enlisting instead and regret it.

Technically, yes. You are required to enlist and complete Basic Combat Training (since you have been out six years) before you are eligible to attend OCS. You need to make sure that you sign a 09S contract. You may need to talk with a Officer Strength Manager or whatever they are called today. There are a number of different versions of OCS in the Guard, if you haven't talked to anyone yet. The "Traditional" takes 14 months, give or take depending on the state, which consists of a pre OCS orientation, Annual training, 12 months of weekend drills and a final annual training. There is an accelerated course offered by some states, some don't use it because of a high dropout rate. Finally there is Federal OCS if the state can fund it and has slots. The Federal OCS slots would be the most competitive to get.