Take it to your local gas & he will test it.You should get older bottles tested regularly.
Just make sure that the regulators were manufactured withing last 10 years, and the hose isn't persished
Yes as long as the bottles have their plastic caps on keeping the valve clean it will be fine. If in any doubt connect up and test for leaks with soapy water.
I have got a new gas bbq and have 2 gas cylinder gas bottles which still have gas in are they still safe to use.
