Restrict certain apps to only wi-fi

[AC Question]

I meed something, perhaps an app, that wil absolutely redteict some apps to run(online) only when the lhone is conmected via wigfi. And I do not mean restrict the app in the background. Completley restrict it. For example I enter youtube when on 4g and the video will never load cause I am not on wifi. I accidently pressed a youtube video and it drained 2.5gb in like 30mins and I have no data usage left...
Thanks in advance.
P.S. I have a non rooted LG G3.

 

[Rukbat]

Look for firewalls in the play store. Some of themn let you restrict usage by app - wifi or mobile data. If you turn them both off, the app can't work at all. If you only turn wifi on, it can't use mobile data. (You';ll usually get a popup from the app about no internet connection - it's annoying, but if the app is written to tell you, there's nothing you can do about it.)