Is there a way to reclassify before my contract ends?

You were forcibly reclassed out of 35L due to academic failure. You are honestly lucky they reclassed you and didn’t separate you. Unfortunately, you are unable to reclass until you are in your re-enlistment window.

With that being said, 37F is consider SOF and you will be required to attend selection, airborne, and the SFQC followed by language training. If you fail language training you are separated.

With all due respect, you were given the opportunity to become a CI agent, which is a pretty easy course to get through, the only real challenge is the 2 year probationary period.

I think you are better off being a 25B for now, learn the army, then re-evaluate what you want to do.

Yes you can. If you want to reclass to 37F there's a selection you have to pass and a Q course you have to attend. But honestly if you failed CISAC you probably will not make it through Psyops QC either.
If you want to attend the selection, contact your local Special Forces recruiter. Otherwise, there are other MOS's you can voluntarily reclass into once you've had a year time on station

Yes. Absolutely you can reclass during the middle of an enlistment period. A few things that you will need to consider.
1. Did you get an MOS based bonus? If so, if you reclass before your contract is up, you may be expected to repay a portion.
2. How much time is left on your contract? Most receiving units will not let you go to schooling if you don't have enough time left on your contract. ( I know you said 5 years, I'm just putting this info out there for the benefit of the group)
3. Do you have an ASVAB score required for the new MOS?

I would find out who your Battalion Retention NCO is and see what your options are.