I'm not sure if we are being trolled here or not, as the OP is all over the place with these questions. If we are not being trolled, the OP appears to have very limited firearms experience.

OP, if you are wanting this rifle for HD, yes, you will need to shoot it to insure that it functions properly and that you understand how to use it. You will need to be able to clear malfunctions... and all of them will have a malfunction at some point. You will need to put a few magazines of your preferred defensive ammo through it too, not just cheap 55 gr FMJ range ammo.

All the technical stuff that you are worried about, such as gas systems... forget about it. At your level it doesn't matter a bit. You need to keep it simple for now. Basic carbine with a red dot and a light at most. I don't even have a light on mine, but we have night lights all throughout our home (and the AR is not my goto HD gun).

I see that you are looking at a 15-22 as a trainer. I would recommend spending that money on ammo and range time, possibly with an instructor over trying to set up a .22lr to mimic your AR. That would serve you better at this stage in my opinion. If you feel you must go with the .22lr solution due to ammo cost, buy a .22lr conversion kit for your AR so that you are still using the same trigger, same sighting system, etc. Less money on hardware, more money for software (training and practice). I read where you think that the conversion kit is "fussy" on ammo... all .22lr can be. Some .22lr feeds better than others in a semi auto. I have both, a CMMG setup and a 15-22... I buy high velocity, bulk pack ammo and it runs fine. I get the occasional dud, but that is typical of .22lr.

If I lived in California, I would not jump through all the hoops to own an AR... I would select firearms that were legal in a normal configuration, such as a pump shotgun or a Mini 14 if you feel like you have to go with a rifle. The Glock you own and a Remington 870 or a Mossberg 500 would be a simple, less expensive option.