State level OCS doesn't guarantee Federal Recognition. If your unit is activated, you are still an officer. If you choose to convert to Active Duty, you won't be. However, it's pretty easy to get Federal Recognition by filling out some simple paperwork. I don't know what it is, but the OCS cadre will.
An ROTC commission is federal.
As a Cadet in the guard, your job will vary depending primarily on your CO. In my company, I've been a PL or a co-PL (attached to an LT, do a PL job when he wants me to) for about a year now. Where I'm at, I'm essentially a 2LT who can't sign paperwork as an officer and who has a funny looking dot on his hat.
Since my unit got activated, I'm now pulling double duty as a PL and the XO. My PSG is a non-MOSQ SGT (came from active duty Marines). It's an interesting situation ... normally my PSG knows his and my job pretty well. This time, we're a little reversed.
That's my bit of rambling.
Oh yeah ... and we get to drink beer at the training meetings