Am I able to join the Ohio National Guard with an RE-4 CODE?

No.

You were medically retired because you were not able to meet the military's medical fitness retention standards. The medical fitness standards are the same DoD-wide regardless of the Services or component (i.e., the standards for the Regular Army are the same for the Air Guard).

The military is required to maintain a list of service members who have been medically retired and these are called the Permanent Disability Retirement List (PDRL) and the Temporary Disability Retirement List (TDRL). In both cases, being placed on either list means that the service member has a 30% or more disabling condition that makes them unfit for military service.

If you are on the TDRL, the military view is "it might be permanent, but it hasn't stabilized yet so we're not sure". As such, you'll have to wait until a determination is made once your disability stabilizes (decision must be made within three years)*.

If the determination is that you disability will be lasting, then you are transferred to the PDRL. If your disability has changed such that you are now fit for duty, you'll be removed from the TDRL and offered to be returned to active duty. If you don't want to do that, then you would be able to join the reserve component as a prior service member.

If you are on the PDRL, the military has deemed that your disability is enduring and will in all likelihood remain so in the future. In other words, you won't be able to meet the medical fitness standards to remain in the military.

It is theoretically possible to rejoin (after going through the process) if you're on the PDRL. You'll have to appeal your medical retirement to the Army Board for Correction of Military Records (ABCMR) with sufficient medical evidence that the medical retirement is in error, and ask that you are removed from the PDRL and that your DD214 be changed to have the RE-4 code removed.
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* Permanent and Temporary medical retirements - https://www.dfas.mil/retiredmilitary/disability/disability/
* TDRL determinations - https://comptroller.defense.gov/Portals/45/documents/fmr/archive/07barch/07b_11_Apr00.pdf

What did the recruiter say? I was also medically retired and unless something has changed you won't be able to get back in. You were medically retired for a reason and unless you on the temporary retired list for a condition that may change over time you are just going to need to find another way to serve.

You would need an Exception to Policy Waiver from Guard Bureau. I don't know that I have ever seen one in anything close to relating to your situation.
Proponent and exception authority. The proponent is the Chief, Personnel Policy Division (ARNGHRH). The proponent has the authority to approve exceptions to this regulation that are consistent with
controlling law and regulation. Supplementation is prohibited without prior approval from the Director,
Army National Guard, ATTN: ARNG-HRH, 111 South George Mason Drive, Arlington, VA 22204-1373.
Interim changes to this regulation are not official unless they are authenticated by the Chief, Personnel
Policy Division (ARNG-HRH).