How does the cash back work it I purchase something with installment on 11street?

Also, how long does supplementary card take to get approved?

as I got the CB already.. how does the usual CB get effected.

For example, if I had outstanding before this RM833.. and now i have rm25 credited, so does this mean i get slightly below rm50 for the regular CB? or if i spend 25 now until CC bill comes out, i get rm50 CB?

thanks.