2. If I don’t use Tesla electrician, warranty on my new model 3 that I’m picking up Monday is void
There is no such thing.
What Tesla does after you buy a new car, is send surveys. They will ask what electrician you used. If you say you used ElectricianX and they did a good job, Tesla will add ElectricanX to their list of installers for others to use.
I know this because the place I used wasn't on the Tesla list, but he was added within the month after I had told Tesla the name and contact info for him.
Unfortunately now that he has more business from Tesla, his install price went from $216 (for my install) to $350 (For my coworker's install who purchased after I did). Once they get more business, they will increase the price.
There is no requirement to use only those listed. It's a standard NEMA 14-50, nothing Tesla specific about it (other than installing it upside down so ground is pointed up instead of down)
My 14-50 install was super simple - the first 2 installers from the Tesla list wanted $500 and $400 for it. So you can see how little I actually paid ($216) by comparison by shopping around first.