Fragmented question?? If you have under 3/32nd's remaining on your tires replace them. If you have wires hanging out of your tires replace them. Replace tires as needed or rather replace all at once if you do not like mis-matched tires. However many people will replace just two tires at a time then rotate when the other two need replacement.
Firestone, Discount Tire, and Goodyear are all great places to purchase new tires. It is advisable to replace all four tires at once in order for all tires to have similar tread and for the car to be able to grip the road most securely.
A tire store will replace any or all of the tires that you want. It depends on how many you want to purchase. They will not try to pressure you into anything you don't need.
Not unless they are all worn out. You can replace just two tires. I recommend you replace both front or both rear tires at the same time. Also make sure that all 4 tires are the exact same size. If the tires are fairly new and not worn you can replace just one tire if one was damaged as long as the size is the same.
Yes only if you change all 4 tires !
It depends on how old your tires are and how warn they are. The front tires will wear out first, so if they replace your tires regularly then you can get away with only replacing the front two. If you rotate your tires when you change your oil or don't replace your tires often enough then you will probably want to replace all four at the same time.
There would be a lot of flat tires.
You should replace your vehicles tires approximately every 60,000 miles. Or when the tread on the tire is close to all gone.
If it is all-wheel drive, then yes! HA! Drive tires must all be the same tread depth. Flatten one, replace 4. Oh, the downers of all-wheel drive!
no unless they are all damaged
if its all wheel drive yes
I would head down to your local tire dealer, who can take measurements of all your tires and give you the required feedback on which, if any, tires you need to replace.