S10e live demo unit repair imei?

Hello everyone!

I’m planning to buy Samsung Galaxy S10e Live Demo Unit, I was curious as I watched a lot of videos on youtube of people repairing IMEI by flashing them, it looks to easy to be true, also I saw few expensive services on Ebay for repairing IMEI for those Demo Units so my thought is that there bigger story behind it, so my question is if someone can tell me is it possible to make it to fully working phone by flashing it or there is some other not so doable way.

Thanks in advance,and best regards to the best community!