Set(o) form queries

Having looked at the forum, and guidance still have a few questions that are confusing

1.4 - Full name - is this just your first name or do you also add your last name( also my surname) here? ( considering Q1.5 is Surname)

5.3- What is your pay each month? My Net has been different every month for the last few months, can i just enter one of them randomly or is this the last month net?

6.2 - Reason for absence, is there a specific wording to use here or is this free form? some of my absence are work related, but i wasn't paid in UK at that time. what do i specify here?

Also Did you have to carry your degree certificates (when the same was used to obtain Tier-1)

Thanks to anyone who have applied and can clarify these queries.