Different rules for applying for Norwegian citizenship apply to people with residence permits in Norway, people who have a residence card for family members of EU/EEA nationals, Nordic nationals and people who have previously been Norwegian citizens.
The applicant is the person who wishes to become a Norwegian citizen.
If you are a citizen of two or more countries, and one of them is an EU/EEA country, please choose this country.
There is no separate application form for dual citizenship. When you apply for Norwegian citizenship, you do not need to notify UDI that you want to keep your previous citizenship. You can read more about dual citizenship here.