Online cessation of auto-entrepreneur activity form?

I am trying to fill the online form for cessation of auto-entrepreneur business (close the business in Francce) and while doing so, I am stuck on some of the things to be filled as below:

1. Number unique d’identification (SIREN). It is asking me for the SIREN number which is a 9 digit number. Is this different to the SIRET number? The SIRET number seems to be a 14 digit number. is the SIREN number linked to the SIRET number, e.g. the 1st 9 digits of the SIRET number is the SIREN number? How can I find my SIREN number?
2. Désignation du centre des impôts où a été déposée votre dernière déclarations de revenus. Can you help me on how and where can I find this information?
3. Date pour une cessation totale d’activite. On the date of cessation, I had already stopped working since mid December but I received my last consultation fees on 12th January 15. If I am submitting the cessation request today, do I need to put a date of today or can I put a date of say 15th January 2015?
4. Option EIRL. There is a check box just below the Date pour une cessation totale d’activite called Option EIRL. Can you tell me what does it indicate and how do I decide whether to choose it or not?
5. Renseignements complementaires.This is the last part of the form where it is asking some correspondence address / contact details. Considering that I will be in France only till mid April and then I relocate outside of France, should I give my France address / contact details or should the details correspond to where I am relocating?

Once I submit the online form, can you tell me as to what would be the procedures to follow?