Yes, if you top up within the grace period, the number will be of course still belong to you. However, if your prepaid number has been expired (terminated) due to no top up within the grace period, then sorry to say, you wont be able to reactivate it anymore.

This is because as per New SKMM rules, any prepaid number activation request must be via walk-in with IC verification. For expired number, their statement is to advise the customer to purhcase the new sim pack with new number. The Digi center staff (my friend) even showed the statement to me which they received from SKMM via email when I walk-in and request to reactivate my expired prepaid number during the past 1-2 weeks...

No... I didn't..

End up, foreigners workers just gonna try borrow IC numbers from sellers to buy instead.