Difference in current name & name at brith

[chandurl]

Hi All,

Need your advice on the below queries for my son.
We received registration certificate which mentions his Full name on the certificate as X Y Z (Z being the Dad's name as the middle name) However they have put 'X Y' as "Name at birth if different" i.e. middle name (father's name) is missing. I see they have taken this name ' X Y' from his Birth certificate.

1)Do I need to do anything about this?
2)Also, while filling the UK passport application form, there is a question 'Have you ever used any other names?' - Should I mention Yes or No?

Thanks