V3, V4 is not matter. some times it is same chip different seller.
just check your chip is MV1-7 flashable. below MV1-6 is not flashable.
MV1-6 is perfectly ok for switch and lite. however for oled you need MV1-7 chip for the better performing.
I suppose your eMMC maker is SK hynix. if so do not apply heat on it. since it is super brittle. Samsung (SEC) eMMC is OK with heatgun. the RED light instead of Green during training session means bad eMMC. (it is not a DAT0 contact problem. it's most likely eMMC got wrong by heat)