Not necessarily. There’s many types of valves obviously, but the most common is W.O.G. (Water, Oil, Gas) used in domestic applications, meaning it can be used for either. Easiest way to tell is the material the rest of the piping is done in.

For example, this looks like 3/8" or 1/2" black iron pipe, meaning it would and should not be used for drinking water, so you could safely assume it’s gas as there aren’t that many different services running through a common household. You can always open it slightly and see what comes out.

All this being said, please for the love of all that is holy, do NOT install your own gas lines if you don’t know what you’re doing! It’s not as simple as running water, gas has a lot more to consider when piping such as length of run, size of appliance(s), and their respective pressure requirements. Call someone with a gas ticket

Not necessarily from the handle. The actual threading on the pipes should be opposite. Lefty tightly, righty loosely for gas. But that assumes it was done correctly and using the correct materials.

That’s not a given, MANY builders don’t follow code and local inspectors will still pass the home with obvious and dangerous flaws because they’re getting kickbacks.

This, so much this.

Hence the word “probable”

I had some people install a new water heater at my place. They turned off what was labeled as the water heater at the breaker and proceeded to change out the heater.

I noticed later that it seemed odd that the AC hadn’t cycled on all day. Eventually realized the circuit breaker was mislabeled.

The guys doing the water heater replacement were working on a live line and I guess they didn’t bother to check with a multimeter. Jesus. They didn’t get hurt/killed thankfully.