Questions about OMSI

I have four questions about OMSI

1. How many diferent persons will be there.
2. In the basic game are first doors for enter and second to exit. Could I set for example all doors for enter and exit. And how passenger will behave in this set.
3. Will OMSI watch configuration of PC? For example if I won't have correct series graphic card or some other component. Will I able to launch OMSI.
4. Could I make train, which will be ride over railway crossing?