Can I apply to active duty OCS while still being part of the IRR?

Yes. Get with an officer recruiter to assess your eligibility.

Talk with your IRR Control Group poc or contact your career manager. They may be able to work with you or you'll have to transfer back to a TPU status and apply from there.

Yeah you just have to talk to a recruiter. You'll have to complete a packet to make sure you're eligible and you'll remain enlisted in your current grade until OCS is completed. You may be attached to a unit temporarily until the next available class begins.