I'm visiting Scotland for the first time this week, Edinburgh. I've lived in the UK for over 10 years but my nationality is Spanish. I only have a Spanish passport.
I'm also traveling by train.
Do I need a passport to enter Scotland and stay in my booked hotel?
Most hotels in the UK do not ask for an ID when you check in, but I think I have been asked for one at times.
If you have your Spanish National ID card, bring that, if not bring your passport.
If you are not happy with taking your passport, call the hotel and ask whether they require it.
There is no border between England and Scotland and therefor you do not need to show a passport there.
Whether you need a passport in the train depends on your ticket. I do not know any train tickets in the UK where you need a passport, but there might some.
If you buy online and have a home print, you might need your passport or ID card, read the print on the ticket.
There are no international borders involved. London to Edinburgh is a domestic train that requires no id unless you're using a print at home ticket.
The hotel is supposed to check and record passport or national identity card information of foreign guests, but in practice this rarely happens.
No and unlikely. Call them to check.
