you've asked two questions with essentially the same answer, you need to directly ask the agencies involved. Not a friend, or a friends' mother's sister's brother's cousin, not the internet, and not a cop on the street,
Not that anyone will deliberately lie to you, but when it comes to these kinds of technical issues with the law, you NEED to go to the source, or pay a lawyer to do so, otherwise you could easily be given bad information in good faith.
Is your TN permit still valid, now that you no longer reside in TN? Probably not, but you need to ask the proper people in TN for the answer. Generally speaking state issued
resident licenses, become invalid when you are no longer a resident. HOWEVER, its up to each individual state, and how they treat the issue. Also, the state has to know you are no longer a resident.
I got a NY permit in 75. At that time, the permit was good for life, unless revoked. In 79 I moved to the west. in 2002 NY sent me a letter stating that since I was no longer a NY resident my NY permit was no longer valid, and, they wanted it back!!! Yes, that's right, they wanted me to return the wallet size paper (non laminated paper, not even cardstock) that they had issued me 27 years ealier! I mention this only for information, but since it took NY a couple decades plus to realize I was no longer a resident, some other state might also not be aware you no longer live there....yet.
SO, if someone from NV calls TN and asks if your permit is valid, and someone in TN checks files that have not been updated, they could easily, in good faith, give an inaccurate reply. AND, if a bit later, TN calls NV and tells them your permit is not valid, NV might be a bit upset with you for presenting an invalid permit. (assuming they care...
)
Second question, will NV recognize my TN permit? You have to ask them. State's recognition of other states gun permits varies from state to state and also CHANGES from time to time. If NV doesn't recognize your TN permit, then it doesn't matter if its still valid, or not, to NV. But, if they DO, then using an invalid permit MIGHT be a violation of law.
CHECK WITH THEM!
Good Luck!