Gauges start jumping around and my stereo stops working?

My scanner won't do some of the relearns. Its an Innova 5610.

I'll see if any come back up.

Can I unplug a connector from BCM to check with multimeter?

I have a security system sensor circuit high code too and a relearn, but it starts up and drives but the 10min relearn doesn't get the light off. My reverse lights are not working either. Well, the bottom ones are but the ones by my taillights are not. The truck release on the driver's side door too. Maybe I didn't get a good enough connection when I crimped the new connectors on. I'll check that one connector and see.

Sorry for asking so many questions, I've been able to drive my car, but the security light stays on, and my reverse lights don't work. My radio and dash lights sometimes don't work. I got a new ignition lock cylinder because the old one is sticking when I start it up, so it'll die if I don't bring the key back to the run position. Could that be causing my lights and radio not working sometimes? It's just confusing me and I'm not the greatest when it comes to electrical stuff.