Does anyone know if you can swap these parts into a 2014 and back Challenger?

The entire front fascia/bumper has to match the grille. The grille opening of the 08-14 is taller.
The 2015 taillights are set in a different rear fascia/bumper than the 08-14 cars as well.
In short, the parts will interchange but you'll need the bumper covers to make it look right.

Kinda thought that. Thanks for the feedback!

Why x9es the hellcat have the old style grill n tail lights? And iv seen a challenger that has the old style grill but the 71 style tail lights
(2015 srt) why are they not all the 71 style?

The rear won't work... tried that. The lights use a completely different wiring setup then 08-14 cars.

Also with the front, the hood needs to be changed as well I've seen. As well as the front facia and other bits and pieces.

All Hellcats have 2015 tail lights and completely unique front ends. It might look like 08-14 grilles and such. But nothing is the same. Everything is unique to the hellcat facia.

Ryan