Only useful if you need or wan't to travel from place to place quickly and cheaply over quite far distances like from cannock to rugely and back
No, it is not. No tilting trains are operated in France for the moment.
It is correct to say "On the train" when you are inside it. either one will work This is also known as being 'on board' the train.
The same things modern trains are used for: hauling cargo and people.
Disel is used by train.