Old gasoline turns varnish like and coats injectors and spark plugs and gums up carburetors. you should dilute with lots of fresh gas or siphon out the old.
You saved a lot of money. The battery may go dead. The gas may go bad.
The car will stop, because the gas will not work until after it is paid for.
Because when you go uphill or put "load on the car" this is when the car will miss under load & "not miss" when you ease up on the gas as you are not stressing the engine. As to why this happens can be many thibgs - spark plugs, ignition coil bad or bad plug wires & many more to many to list here
When the mass air flow sensor is bad you will have a rich smell in you car. Additionally, your car will consume more gas as you drive it.
When you have a bad oxygen sensor your car may consume a lot of gas. Your car may also drive slower.
EGR Valve
car smells of gas inside and out
bubbles
This is BAD. You must not try to run the car, if the bleach gets into the engine then it will cause serious damage. Yo will have to have the gas tank replaced.
check trans mount or u joint maybe you have a hanger bearing? and its loose in the rubber? dent in drive shaft? or a bad drive tire?
When an O2 sensor is bad your car will not run efficiently. You will use more gas than you would normally use on a trip.
If you can drive the car you can pump the gas.