Does having RA at young age will lead to eqrly death...Than having RA at an older age?

Disease mortality. The longer you have ra, the longer the disease (or RA medications) can damage your body. The good news is, that with newer, more effective treatments there is good reason to be optimistic that the RA can be well controlled, leading to a productive life with a normal life expectancy.
JRA is different. Juvenile arthritis is different than the adult form of rheumatoid arthritis. There are different types of juvenile arthritis. The type of juvenile arthritis that can affect the internal organs and cause more long term problems is systemic arthritis. The other forms of juveile arthritis typically affect the joints and the eyes.