Applying for ILR after 6 yrs in Discretionary Leave

[Rash456]

Hi
I am planning to apply for ILR Under 6 DL category.
Myself, Mrs and children got initial grant in 2012 Feb. Children are born in UK,

Looking forward answers for the below questions:
Greatest appreciate your time.

1) do the Life in the uk test pass certificate is compulsory, if not can we leave ticked 'No' for section 4.3 in SET O form,

2) not planning to include children in the form as they born in uk, however should I state about children in the cover letters as basis for DL was family life.

3) what are the documents required to submit, when applying from DL route.

4) finally, only have a photo copy of initial DL approval letter from HO. Does this matter?

Regards