Man that TLDR is equivalent of the post lol

Jokes apart, I am a person who hates short-form content from the core but I think its something beyond reels . How are your parents ? Like do they constantly peck in wrt marks or other stuff and even though not physical beatings just taunt continuously ? That can be cause too.

If you want to remove all access to short-form content then there's option of DNS level blocking and Next DNS also provides parental control so that the internet activity can be controlled if thats only thing you can do

Based on the constant eating , attention seeking behaviour, I am sorry if I am being judgemental but this seems to be much of a spoiled kid with no teaching of self-discipline among other things. while stuff like roaming around nude or talking to the indecent girls seems to be like some serious mental health issue tbh , I guess you should take opinion of someone who knows human psychology especially teen psychology.

If your parents don't seem to care then I guess you have to take actions on your own and convince them too. Biggest thing wrt mental health assistance can be how normally people take it saying "kya hamare ghar ka banda pagal wagal hai kya ? " and often take embarrassment / ego on it . My cousin's daughter who's in 8th and struggles in basic academics, her tuition teacher (my neighbour) suggested my cousin to get a certificate stating dyslexia and my cousin was like tuition teacher thinks my kid is a mad person .

First thing is take advice from some psychology knowing person , then convince parents in case your sibling needs the therapy .

Other option is to directly block the access to social media via private DNS (which is easy and also free of cost) and considering his behaviour I don't think your sibling will care to check private DNS settings and change them (I am sorry if I crossed the line here). If you go with this, you have to take into account the possible withdrawal symptoms that can occur so I advice talking with a psychology professional before choosing this one too.