Just create today?
If i'm not mistaken, number need to be 30 days with 1 telco before can port to another telco.

There is a one month cooling period for all operators if you mnp over. Which means, you have to wait one month before you can port out to another telco.

The easiest is port celcom to hotlink prepaid 1st.
Once successfully become hotlink prepaid, same day u can just go to maxis and request them to change the prepaid number to be your postpaid supp line.

yes any postpaid or prepaid can port to hotlink prepaid.

and yes celcom postpaid is pay-1st-before-use means u are actually paying monthly in advanced.

example statement 2 feb is for usage on 2 feb till 1 march (compare to maxis as example, statement 1 feb is for usage on 2 jan till 1 feb).

so if like that, u better port out 1 week before your 3rd statement date