Cover Letter & Step 1 of Appointment booking

Hi All,

I have completed 5 years in Tier 2 ICT category last month and now am looking to apply for ILR in person. I have cleared the LIUK test last week and am planning to use the PBS calculator along with my Original Degree ceritificate to show my English qualification. I have also got the letter from the Employer confirming my employment details and absences. I only have a gap of 15 days in visa after 1st year, but I think, that's covered as part of 28 days policy under 'Continuation of lawful leave during absences from the UK' section.

My question is, do I need to write a cover letter or something to brief my case or it's not required as the SET(O) Form has all the details and I am submitting all the required documents?

Also, when I tried to book the appointment through UKBA website, it asked me to choose the type of applicant from the options like,
1. Tier 1
2. Tier 2
3. Other main applicant
4. Dependent

Since I am currently on Tier 2, Do I need to select Tier 2 or Other main applicant as I am applying for ILR anyway? This is bit confusing.

Thanks for your help

Sri