Queries on SET (LR) form, section 4

[JITL]

In new SET (LR) form (issued in April 2013) , under section 4 for documents required (page number 19), I have following questions and will be so grateful if somebody can kindly respond with answers:
•Gas, electricity and water and other domestic bills or statements for each year of your stay: How can I obtain these? I have also lived in shared accommodations several times and did not have accounts on my name.
•Employer letters confirming dates: I have old reference letters from each of my previous employers with dates, can I use the same letters or do I need to request employment letters now again with current dates?
•Letter from landlord confirming the period of tenancy: Is this only from the current landlord? Or do I need letters from all previous landlords too?
•Dept. of work and pensions letter or other letters from other departments or agencies: I have never claimed any benefits etc, do I still need letter from Dept. of work and pensions to confirm this? What can be other departments or agencies?

Many Thanks in advance