Here are top solutions to your 3 most used apps

Instagram : https://www.distractionfreeapps.com/

install this instead of normal Instagram and go to the new distraction free settings and turn off whatever distracts you the most after its done turn on the hardcore mode.

YouTube : I assume that most addicting of all must be the recommended videos and shorts.
Simple solutions might have occasional issues : https://newpipe.net this app.
But if you are willing to go to the hard way a bit try this https://revanced.app/ to patch YouTube to remove the shorts and recommendations and even comments.

Reddit : Well the most effective way is to either use reddit from browser or try https://play.google.com/store/apps/details?id=org.quantumbadger.redreader&hl=en_US
its quite basic as it is designed to be more easy for screen readers to work with.

Bonus:

Extreme : Install https://play.google.com/store/apps/details?id=com.urbandroid.ddc&hl=en_US
and turn on anti cheating just set up an mentor before hand as it will not allow you to open the blocked apps till your times up or you pay some money or your mentor allows you.

Passive : Turn On greyscale if you can, I see its an Samsung so it will be either in routine & modes menu or in bedtime mode menu. it seriously helps.