If it was not equipped with seat belts when it left the factory new, it is not required. That is in the state of Connecticut, USA. Check with your local DMV.
Not if they did not come from the factory with seat belts. If they came form the factory with seat belts you are required to wear them.
Children up to certain weights are required to be in car seats that are held in place with the seat belts in most states. After they reach a certain weight, they are required to wear seat belts, so not only can children wear seat belts, after they no longer are required to be in car seats, they are required to wear a seat belt.
a seat belt for each seat
The 1965 came with lap belts for the front seat only. This was a new law for 1965 and only required front belts.
If the vehicle was built with seat belts you have to have them but if it didn't have the belts from the factory your not required to have them.
Everyone
Everyone
Whatever the vehicle came with when it left the factory is what is required.
...save lives and are required by law.
Seat belts were invented in the 19th century by the English engineer George Cayley, but were not required to be installed in new cars in the US before 1959.
Seat belts are legally required in most jurisdictions. Wear your seat belt.