First- Ohio State law appears to permit Class III sort of things as long as you meet Federal laws.
Federal- you cannot make a full auto. Only those already registered by May 1986 CAN be registered to a private citizen.
Building an AK74 pistol (semi auto) Have fun. Federal law allows you to build for your own use, SN not required.
Suppressor- transfer must be made thru a dealer in your state with the right licenses. If you want to MAKE a suppressor, see the ATF, pay the fee and do the paperwork FIRST. Same for making an SBR.
Adding a stock to a pistol- makes it an SBR. See above.