yes

Is true in some sense, but to make the cash back effective and you can get full rm100 all the time, the cash back are calculated based on transaction posting date.
And for each transaction to be posted, it will be T+1,2,3,4 and sometimes can take up to 9 days. Merchant are not fooling around with this as they are doing daily closing, more on the terminal and HLB fooling around with this. So last transactions shall be done 5-7 days before.
CS never wrong, just that you need to understand how they play their game, as they are paid to mislead you.

it depends on individual experience. i swiped on 30/1 at jaya grocer and it got posted on 31/1, even though both days are on weekends.