Question [Q] replace camera app

before I upgraded to Blue Lightning Rom I had a more recent camera app version. I wouldn't say I liked the interface changes (tap screen shutter suxx IMHO), but I lack know the HDR wich was present in it

Is there a way for:

a - run separate camera app simultaenously?
b - flash between them (less preferred)

if only the latter is possible, is there a place where both the JB and KitKat versions can be found/DL-able (say without anything else(no gapps, just the cam app))?