Can I sell an iPhone 6 Plus after reporting it lost?

So I reported my iPhone 6 Plus as lost and I got a new one through my insurance. My question is if I sell it on eBay or go to a pawn shop and sell it will the next person who buys it be able to use it. Also I reset the phone to factory settings.

That's called fraud, and it would be found out when the next person in possession of your "lost" phone tried to activate it. That's why phones have serial numbers, and phone companies do take these things seriously.

The IMEI is blacklisted. It can't be reactivated.

No, once its reported its now blacklisted and can no longer be used as a phone. It doesn't matter if you reset it or not, the carriers control that. You could probably sell it as an ipod touch and clearly point out its been reported lost and can't be used for phone calls, obviously the value goes way down but that way you get something for it (better then 0) and the person knows its no longer a phone up front so they don't show up at your house with a baseball bat.