Verizon branded phone on Sprint

I have an old Verizon flip phone that has active service with a Sprint MVNO. (I checked the number on freecarrierlookup.com and it shows it is on Sprint.) I believe (though aren't certain) this was done by flashing the Verizon phone to work on Sprint's network.

The phone was given to me with active service that's expiring this week. The account is not in my name. I'd like to wait for it to expire and then use this phone to sign up with another Sprint MVNO.

Is it safe to assume that once the old provider's service date expires that this phone will be available to use on another Sprint MVNO?

Another hitch is that in the phone settings I can only find a MEID. It is in hex format. I don't see any IMEIs or any other identification number. Tello seems to recognize the hex MEID and says it is currently in service with another provider but Ting's lookup tool as well as any other IMEI/MEID lookup tool I've checked says it is an invalid ID.

TIA

Is the phone 3G only? If so, to speculate, maybe Ting's and similar checkers no longer accept activations of 3G Sprint phones, whereas, since Tello still sells at least one 3G phone on its site and its checker accepted your phone, Tello still accepts activations of 3G phones, unlike some other MNVOs.

It's the LG VN150 flip phone. Which is certainly no more than 3G. The warranty date listed in the settings states 2012. (Not sure if that's the start date or end date.)

Have you tried converting the ESN/MEID from HEX to DEC? There are calculators online that do this.

If service provider has grace period, device/number may not necessarily be released until service is actually terminated.

If there was a donor device used when flashed to Sprint, the ESN in settings is cloned.

Unknown if donor ESN still eligible for new activation until existing service terminated.

If device does not support HFA, manual programming may still be possible (with MSL) for voice/text.

Unknown if flashed/cloned device uses donor MSL or something else (eg; all zeros).

Can a Sprint MVNO (not owned by Sprint) place a subsidy lock on a Sprint handset, preventing it from being used with a different Sprint MVNO?

Yes. But only if by "Sprint handset", you mean a handset that works on the Sprint network.

Example: FreedomPop locked the handsets they sold to use on FreedomPop for x (I don't remember how many) months.

If by "Sprint handset", you mean a device originally sold by Sprint Postpaid or Sprint Prepaid, I do not believe an MVNO has any capability of locking the handset.