If I switch to a new phone and transfer my old number to it, can I at a later date reactivate my old phone with a new number for someone else in my family?
As long as the phone isn’t a Defy, the answer is yes. The old E1,E2,G1,G3, X1 and X2 phones can all be reactivated along with all the new phones.
So long as the old phone isn’t a DEFY XT, yes: Reactivating My Republic Phone.
All legacy phones except the Beta Defy phone, cane be reactivated on a 2.0 plan for a new line