Passport application questions

I wonder if anyone knows anything about below:

1. Confirm identity - what info does my friend need to know about me? only my dob and address?

2. Will I need to include an envelope for return documents in the parcel?

Many thanks

1) https://www.gov.uk/confirm-identity-onl ... s-identity

https://www.passport.service.gov.uk/confirm-identity

2) No. You can however pay £5 for secure return when you apply.

Many thanks!