There should be a shutoff at the wall where the water line enters the house. There may be one before the water heater or there will be one at the water meter.
You will have a shut off for the commode and each sink. The only way to turn the supply to the shower is to turn off the supply to the entire home.
YES and No Yes if you are going to be working on the gas water heater and No if you are working on a cold water line and if you are working on a hot water line you can shut off the gas or electric to the water heater so in case your water heater drains but what I usually do is just turn the water heater's water supply valve off.
Without having a stop in the run you'll have to turn off the system, unless...If it is the hot water side you can turn it off at the water heater.
Most tubs do not have a shut off in the supply lines to it. You have to shut the main off where it comes into the house.
no
Turn off at curb stop to decommission whole house or building. Inside of house or building, turn off valve at main water supply at meter and cut and cap cold water line to be decommissioned.
you have to turn off the supply and its usually a valve under the sink. if no shutoff there then turn off the main valve which is usually at the street at the meter box.
Turn main water supply off in your basement. Adjust or replace shower shut off knob.
Check if the water supply line valve underneath the sink is on or off .."On" will be turning counterclockwise ,If not look for the hot water heater and make sure the water supply valve is turned on.
As long as the water doesn't drain out of the heater somehow, no. What kind of car are we working on...
I did some research regarding your question and the type of shut off valve you presumably have installed is called a ball o stop. these types of shut off valves are turned off by turning the handle a quarter turn see manufacturer website below and email them directly with further assistance
It could be as simple as air in the lines. First thing I would try is: Turn off the main water supply coming into the house. Then turn on all your taps while the water is turned off. Turn the water back on and start at the farthest faucet from the main and start turning taps off. Work your way back towards the main until you are done. Hope this helps.