As long as you have paid any bill he has no right to hold the car. If he wanted to go to the trouble he could call law enforcement and they could probably give you a ticket, but unless it is truly a danger to the public, I doubt they can keep you from driving it.
Your alignment is off. Take to mechanic to have it re-aligned. Inexpensive to correct. Low tire pressure? Loose steering component? Bent component?
As soon as water in seen in the oil reservoir it needs to be taken to a mechanic immediately. Further driving will cause the head gasket to blow.
call a few of your local used car independent lots they usually can recommend a mobile mechanic.
If you have a bad shift solenoid, DO NOT DRIVE THE CAR!!! The shift solenoid may get you around but only for a limited time. It could actually go out at any time. Your best bet is not to drive the car at all...not even to the dealership or repair shop. Not only can this leave you stranded, but could cause an accident on the hiways or city streets. Think safety first. I would have the car towed to your mechanic rather than drive it there, if at all possible.
if it is a result of the work that the mechanic in question performed
I don't see why not. Same for any other car, truck, suv, van, bike, anything... But it's probably illegal, unsafe, and possibly bad for the car. But I'm no mechanic.
Unless you have had the problem corrected by a certified mechanic, or have been told its okay to drive by a mechanic, then I would not recommend it.
For more experienced drivers it shouldn't be, but for some youthful drivers any distraction could be unsafe.
If you haven't paid for the work done to it, they can place a mechanic's lien on it.
drink beer, text, and fall asleep
Yes
If the brakes are out then you have no business putting it in any gear because it is unsafe to drive a car with no brakes.
Only if you don't pay.
Take the car to a mechanic or a mechanically inclined friend to take it for a test drive.
It is true that if the mechanical shop is holding the car because of non-payment of the repair, they would need to have filed a mechanic's lien on the vehicle in order to legally detain it. However: If your complaint is that the car was not fixed properly you shuold have taken the mechanic to small claims court, rather than just not paid him.
If the consumer has not, or refuses to, pay for services rendered, the mechanic can hold the car for collateral reasons. If you want the car back with the repairs done, then you need to pay the amount due. The mechanic has bills to pay, too.
They may become unsafe to drive due to rust weakening parts of the car.