CAR WON'T START. NOT BATTERY. CHANGED FUSE AND RAN

hmm try to check all bolt and pipes

Spray starting fluid into the engine air intake, if it fires up and dies you have a defective fuel pump most likely.

CHARGE THE BATTERY WITH A CHARGER AND FIND OUT WHAT IS ON DRAINING THE BATTERY OVER NIGHT

It sounds to me that your engine shut itself off when it was overheated. If that's the case then you are looking at a major engine repair based on what you are telling us.An engine that gets hot enough to shut itself off does serious damage internally before it dies. You will need to take it to a shop to a complete diagnosis. Hope this helps.

did you reset the alarm/immobiliser system every time the power was disconnected???

I think you are absolutely right. Some of these autobody shops hire monkeys that can barely tie their shoes. They forget things like tightening battery cables and they fail to anchor down wiring or even inspect it for damage. They want the car in and out so they can make more money.
Yes there is more possible damage, though the car accident may have caused it. Your locks should work regardless of the key position. As should your interior lights. Start with checking the fuses and hope you find it there. Something also might be burned out in the ignition switch cutting the power to the locks and lights in the off position. Not really sure how that one is wired up to be honest. Really hoping it is just the fuse.

under what condition the car won't start?
is it when the car set over night, a few hours or after a few minutes.
does it make any noise or click when you try to start?
does the engine even turn over at all or just silent?
if nothing happen then may be the starter, switch or fuse.
if the engine turn but won't run then may be the ignition system or fuel system.

sounds like you blew a head gasket or cracked the head it will be expensive to repair. anytime you have white smoke coming out the exhaust you have water in the conbustion chamber.

Sounds like something shorted . Fuse is often in there for such long periods of time that it can get stuck. At this point give the man some time to do a diagnostics without "second guessing" him. Sometimes things happen and although the timing of the failure appears suspicious, it may not be...(Once had a timing chain on a customers car fail after an oil change while it was backing out of the shop...routine job...just happened that way!!)

depending on the year model of your car the voltage regulator is intergrated in the pcm