checklist and address questions

i came across a few questions, hope the answers help others as well.

1) in the Appendix A checklist it says to send in 3 copies of form schedule 1 background/declaration. and on form 5491 document checklist it does not mention 3 copies, which one is correct? one or 3 for each person over 18?

2)Imm5491 #17 and 18 it says sponsor must submit option C print out and a letter from employer, if its family class sponsorship and we are excempt from the income guidlines why do we need the option c and letter from employer?

3)my brother ( who is not comming to canada except to visit one day) has a P.O box which he receives mail at and his house address does not receive any mail at all (its in the desert in san bernardino california-mohabi desert)and the form Imm5406 asks for addresses of all my siblings, which should i give them? P.O. box or non mailing house address? If they mail anything to his house address then he won't get it.

i thank you all for all your help.