@PM10Plan
Yes, you can do both actions and won't affect your current reward. You will still stay on the old rewards system with those changes
order doesn't matter
1. For porting, make sure the other account on the other provider is still active You DON'T have to do anything to close that account. Once the number is ported, that account will be closed.
You request porting via My Account, Profile page and Change phone number, then request Transfer in. It is better to use the Account number of the other provider as the porting information.
And remember to have the other provider sim card in a phone. After you request porting, the other provider will send you a text and you need to reply YES.
Then on PM side, reboot your phone every 30 mins until you receive incoming calls for that number on your PM sim card
2. it is better to schedule plan change on renewal date as unused date on the current plan will be forfeited if you choose Change plan now. But there could be issue if PM pull this deal out before your scheduled plan change date. It is true that PM should honour it anyway, but there had been argument in such case before