I can use Slide Over, but not Split View. Can I modify any plist files or do something in order to be able to use it on my iPad mini 2?
There's really nothing that you can do to change that. iOS is not open-source, so users can't change source code. But it's also hardware limitations, so even if you were to find a way to force Split View multitasking into your iPad Mini, there's no telling what would happen. Apps would likely randomly crash, if they were even to open in the first place. Apple does a great job of supporting older hardware, so if Split View was feasible to implement on older iPads, Apple probably would have done it.
Install Medusa tweak from Cydia and you will get real splitview multitasking.