No visa for the countries of the European Union: valid identity card or passport.
It is not possible.
With the Romanian identity card; also possible with a passport.
An identity card is sufficient for a Romanian citizen.
No, because Montenegro is not a member of the European Union.
of course you can, Poland and United Kingdom are in European Union, so the passport is not necessary, polish ID or british ID is totally fine
An identity card is sufficient.
No, you need a valid passport.
For a Greek citizen: identity card or passport.
No you cannot enter without a valid Romanian Passport
All Pakistanis do have a National Identity Card (NIC) and they are required to carry it around whenever they travel.
Yes, You always need a passport (or EU national identity card) to get in our out of the UK.