I am in the process of submitting my spousal sponsorship application soon 
These 3 may be silly questions I am asking. But, I heard of CIC returning application forms where they see blank for some sections, so better being safe than sorry.
1) Question about Generic form (IMM008). For the "Contact information" section, there are boxes for P.O.Box and Apt/Unit, which are not applicable to my wife. My wife tried typing 'N/A' for the P.O.Box, but the form fails while validating. So, my wife left P.O.Box and Apt/Unit as blank instead of writing N/A. How do you guys respond when you did not have any Apt/Unit #? Left it blank or wrote N/A?
2) On her IMM5490E (Sponsored Spouse/partner questionnaire), she left blank for questions 20-23 (not even writing 'N/A') since we both are married, and not fall into "Common-law or conjugal".
3) Also, I am looking at the checklist IMM5491E. For item 19, since I believe there are no minimum necessary income requirements for the spousal sponsorship, I am leaving it blank. Similarly, item 20 where it says "If you are a Canadian citizen living exclusively outside Canada.." and so on. Since, I live in Canada, I plan to leave this blank as well. Did you guys just leave them blank OR write N/A when they are not applicable to you ? If you wrote N/A, did you write it on the checklist box itself?
Since the form does not mention anything about writing N/A in these, we are leaving these blank for the 3 points I mentioned here, but want to know your inputs too.
Thank you.

These 3 may be silly questions I am asking. But, I heard of CIC returning application forms where they see blank for some sections, so better being safe than sorry.
1) Question about Generic form (IMM008). For the "Contact information" section, there are boxes for P.O.Box and Apt/Unit, which are not applicable to my wife. My wife tried typing 'N/A' for the P.O.Box, but the form fails while validating. So, my wife left P.O.Box and Apt/Unit as blank instead of writing N/A. How do you guys respond when you did not have any Apt/Unit #? Left it blank or wrote N/A?
2) On her IMM5490E (Sponsored Spouse/partner questionnaire), she left blank for questions 20-23 (not even writing 'N/A') since we both are married, and not fall into "Common-law or conjugal".
3) Also, I am looking at the checklist IMM5491E. For item 19, since I believe there are no minimum necessary income requirements for the spousal sponsorship, I am leaving it blank. Similarly, item 20 where it says "If you are a Canadian citizen living exclusively outside Canada.." and so on. Since, I live in Canada, I plan to leave this blank as well. Did you guys just leave them blank OR write N/A when they are not applicable to you ? If you wrote N/A, did you write it on the checklist box itself?
Since the form does not mention anything about writing N/A in these, we are leaving these blank for the 3 points I mentioned here, but want to know your inputs too.
Thank you.