have you made any previous uk immigration applications in the uk or abroad

Hi. I am applying for the British citizenship and I need some clarification regarding the question regarding the previous UK immigration applications. Just wondering if someone's could advise if the application for a Registration Certificate(Ywllow Card) for the Romanian and Bulgarian citizens counts as Uk immigration application and needs to be stated when answering this question. I applied for one back in 2011, but the work restrictions for Romania and Bulgaria have been lifted in 2014.
Any advice will be appreciated.

I think that question is just about visa applications/EUSS applications, registration certificates are not immigration applications to my knowledge. You can omit that.

It would make sense for me too I am just in doubt, as the UK Border Agency is displayed on the paperwork.

Even so, it doesn't affect your statutory requirements. it is a question only to check their records are correct. You can declare it if you wish, there will be no visible consequence.