Question about tweaking YouTube etc

Hey

When I was using a iPhone for a bit with jailbreak I could download some tweaks like..

Adding a download funtion into the stock YouTube app

Reverting to the old theme of youtube

Or download option in instagram stock app

I know there are 3rd party apps but is there any mods or tweaks where I can download videos in the stock app on the note 5?

YouTube app

Hı Guys
I've tried almost all ROMs for Xperia ray on the phone. But none except cm12 legaxyxperi to 480p video on YouTube could follow .
I watched the other ROM max 360p .
The problem stems from what you think .
Gapps , Kernel, data storage
Many thanks for yours ideas:o:o