I am currently on the 12-month inner circle plan.
I am using a refurbished iPhone 6S that I purchased from Virgin Mobile.
How long does my iPhone 6S have to be with Virgin Mobile before I can:
a) use it on Sprint?
b) use it on a Sprnt MVNO, such as Tello or Ting?
The policy for a domestic unlock is 12 months of service regardless of where the phone is to be used.
I was able to perform a domestic and international unlock of my phone after 14 days.
Does it mean that I can use it on Sprint or a Sprint MVNO after I leave Virgin Mobile or do I have to wait for 12 months before using it on Sprint and/or a Spring MVNO?
If you have already unlocked your phone both domestically and internationally then you are now able to use it on any carrier that accepts it.
Since the Inner Circle is a prepaid plan you are free to terminate it at any time without penalty and take the phone wherever you wish.
You could check the unlock status on a variety of carriers right now: AT&T, TMobile and Verizon right now by going to their websites and entering the IMEI.
You could also check on Ting or Tello on the CMDA side and should get a message that the phone is currently activated but can be transferred. On the GSM side, Ting should indicate it can be activated immediately.
The Sprint BYOD checker would also likely indicate it is activated but you might need to contact customer service to determine its eligibility.