Today I got a mail from the CIC with the request for additional documents form CIT 0171 full RQ

, I'm gathering the documents again ( since I sent all of them for the CIT 0520), but the only odd thing is that they're requesting the supporting documents covering 4 years from the date I submitted my application of the citizenship, the issue is :
1- I applied under the old rules (3 years) and the forth year I haven't immigrated to canada yet.
2- should I provide anything for that 4th year from the country I was living in before Moving to canada?
3- should I attach a letter of explanation to the CIC officer that my application was submitted under 3 years rules?
Any help or advice about the documents to provide for the RQ or answers to the questions above, will be much appreciated.
Thanks,