1997 jeep grand cherokee limited battery getting drained and check engine light on?

Bad batteries can cause all sorts of problems not least incorrect codes. The first thing you MUST do is the charge the battery fully using a mains powered charger then get the battery properly load tested. If the battery is bad replace it. If it is good get the charging system checked. Only if the battery is fully charged and known to be good should you think about any other electrical problem, including the O2 sensors.

The radio might just be a blown fuse check the engine bay and cabin fuses. If they are good and it's an aftermarket radio it may have a fuse in the back of the radio or one of the wires from it.

Chrysler vehicles will activate the check engine light if the alternator is not charging properly. If the alternator is not working your battery will die all the time and you will not have enough juice to run any accessories. I dont think it takes a genius to figure out where im going with this. But do change that O2 sensor if it keeps coming up after you change out the alternator and/or battery cause they will affect performance and gas millage significantly so its worth the $65.

For your dead battery problem do a power draw test, I do not recommend disconnecting the battery to clear codes, doing that causes voltage surges and can fry you computer if you do it enough, It may be the upper or lower bank. left or right O2. that you have to figure out, and if the light is coming on right after the battery is unhooked the connected and the engine isnt even warmend up, then it could be a ecm or O2 heater problem, you need a qualified mechanic to look at it or take it to the dealer