Do I have to go through S2 to renew my security clearance? Are there other ways to renew?

As an MP, you need to ensure that every member of your Chain of Command and NCO Support Channel are aware of your situation because no Security Clearance = NDMOSQ. If you received an MOS based bonus, this may affect you adversely as you will effectively be Non-DMOSQ once your clearance expires. Since it will affect your Commanders USR, he/she will have a vested interest in making sure you get in contact with someone.

What do you mean they are unreachable? If it's time for you to renew your clearance S-2 should be looking for you. If they have not contacted you, or are not available go to your BDE S-2.

You can do the background information by paper, but it still has to go through S2. They have to justify why you have to have a security clearance. Not sure why the S2 is unreachable, but you do not want your clearance to laps. If it is does you are qualified to sweep floors. Not only that, everybody down the chain is going to hear about it. So if this is 3 months or less out you need to start letting somebody in your chain know because the 1SG is going to be looking for answers on who screwed the pooch.

I don't see how you could otherwise... Though not the S2 officer personally if that is what you mean, your security manager AT the S2 shop is going to be your POC, best I recall. And from my experience, it was never the S2 officer anyway, from BN to CORPS level, the security manager was an NCO

I would say no. I would make an inquiry the the NCO in charge of your S2 shop. You could push it up to the BN XO for feedback.

It has to be done thru your BN Security Manager. And since they work in the 2 shop....yep.

the S-2 is the Primary maintainer of security Clearances at Your Local Level so you are going to have to go thru them

Your S2 should be tracking and have sent you a link though OPM in order for you begin, 30 days before it's expiration date. I would highly recommend that you have all the information needed to complete it BEFORE you initiate it. You have 5 days to complete the questionnaire, of not complete, it will lock you out. Also your best option is tell your PSG to walk down to your S2/ security manager to get that started. If your unit treats you like big kids, then walk down yourself and let them know. I just renewed mine about a month ago and you cannot submit it on paper, it has to be done on the Digitl SF 86 through the link you are given. Hope this helps out.