Global pass- can I only travel in one country or in 2,3,4,5, country of the 33 possible?

Thank you!

Another question: can I buy 2 pass for 2 other persons? I mean, it’s not nominal? 

thanks

If you know the names of the travelers, then you can. But you can’t change the travelers name on the passes later...

Is it mandatory to plan our trip before? 

For example, I want to visit England but I don’t want to do a “road trip”, but to be based in London and have some day-trips in other cities. But the problem is that some of the cities are not addable (I can’t add them) to the trip (eg: Bath, Bournemouth) so does it mean that I can’t travel there with the pass? 

The rail planner app doesn't limit in any way the validity of the pass. Bath (the station is Bath Spa) and Bournemouth are in the app but maybe you need to update the app? In any case, if any train that is missing can be added manually.