what diagnostics can be done before pulling the bumper?

2013 CTS-V 6-Speed sedan
I have been sitting in a drive-through for about 15 minutes with the car running and go to Take off realize I dropped my drivers license, as soon as I put the car into gear I go to leave again come to a stop sign take off go to shift into 2nd and it was not possible so at this point I realize there's some kind of a issue, wiling neutral I tried to and shifting the car into first gear when into a fine tried shifting the kind a while in neutral I tried to and shifting the car into first gear when into a fine tried shifting the car into 2nd and was unable tried shifting into 3rd and was able, tried 4th unable 5th was able, 6th was unable reverse I was able to shit into (all while parked) so at this point I turn the vehicle off restart it and repeat this process again no changes so now I decide I'm going to limp the car home and take it to the dealer in the morning, once I got it out onto the main road and got it into 3rd gear while driving along at about 50MPH I kept pushing the clutch to the friction point as soon as it would start to grab I would let off of it I repeated this about 3x when I had came to the next stop sign all gears worked fine almost as if the sink roads were bad however the car only has 14,983 miles and since this issue I have had no problems like this occurred again any help would be great, or maybe even just some suggestions thank you kindly for reading this post..

When I'm driving it goes bck up. I have had my oil change so that's not it. Why is this happening

Had fuel filter replaced and other stuff, like plugs. Could it be the wires? Not sure. It has 190,000 miles, well taken care of. Oil leaks below engine, cannot afford to have it fixed. Am disabled vet, this car has to last longer. Returning to show next Tuesday, any suggestions?
The missing usual around 55-60 mph. If I floor it, it does not miss. At times up small hill, and other times on level ground. not all the time. Filled with premium gas it seem to help.

shifter pops out of reverse every time and occasionally in 2nd. im thinking a bad clutch or worn shifter - i don't think the tranny is going bad.

The car set locked and now we cant get in to charge it.

the theft light came on and then a msg came on that said service theft system. then the car would not start nor will my key come out the ignition. i had my car towed to the nearest dealership who kept my car for a week and tried fixing other things unrelated to getting my car started. all i want to know is what should i do when i tow my car to the next shop. what does this sound like to you?

does my caddy need a clutch fluid drain and replacement at 22k to make clutch more smooth even though it is 5 years old?