It actually is okay to lift weights at your age. I am a 14 year old girl and i bench press a bunch of weights and i have not stunted my growth. Guys are mad to lift weights I'm not suppose to lift weights but i am strong enough to do it. The answer to you is yes.
Ideally, individuals over 65 years of age should not lift weights. As one ages, muscles and bones weaken and it could be easy to damage or cause injury to oneself.
If they want to lift weights it's perfectly fine. It's not like smoking, in weightlifting you can start at any age ;)
Depends how much they weigh and how strong they are
No, it is not advisable for 10-year-old boy to lift weights because of skeletal immaturity at that age. Wait until age sixteen or 15 at least.
It depends on how large the weights are....
Yes, this is old enough. Lifting will not stunt your growth as the myth grows. Just make sure you do it correctly, and get supervision at first.
I would wait until you are 12 yrs. old to start.
The perfect age to build muscle is 18, but you can start working out at 16, though it is not recommended that you lift heavy weights or weights you're forcing your body to lift.
65 is a great time to get started. I would just get a trainer for a session or 2 though to show you how to do things correctly, and especially make sure you are healthy enough to do it. But muscle strength is important when you get up in age just for quality of life.