How much is the average daily screentime

We're in the information/automation age, everything requires screentime , you want to learn something new? Online course. Simulate circuit , conduct mechanical analysis? Software simulation etc etc.

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if possible the scope in that branch in future

Branches don't actually have scopes , field and domains have scopes. It's just that everything is getting automated so if take Cs/IT you get a job , it might be shit or good but you get one.

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Plus my interest is in making things like robots, drones and stuffs. AI

I am presuming you don't know what that entails. So :

AI is a field of Machine learning which is a field of Data Science which is Statistics admixed with Programming.

Robotics is a combination of Mechanical , Electronics and Programming , you'll probably have a course on 'Mechatronics and Robotics' depending on college/branch. You ideally want Mech,Elex or Cs/IT.

Mech - Only if it's top tier. Also Mechanical isn't going to teach you much or rather anything about robotics other than well Materials and Mechanical Physics and maybe if you're lucky basic electrical and programming , you'll have to learn yourself, don't take mechanical ,the top comment guy did the same.

Elex - This is better , electrical circuits are in every robot and more importantly Microprocessor/controller structure , you still need to learn programming but at least you wouldn't shit yourself when looking at a 32-bit microcontroller design.... maybe.

Cs/IT - Ideal , you will need programming both at basic and sometimes advanced level. You'll also probably have Computer Architecture, Digital Communications , Embedded Systems, Robotics itself as well as ML/AI.

TLDR : CS ideal , Elex good , Mech mediocre to bad.

Also , if you want to get experience/headstart , google what an 'Arduino microcontroller' is and what we do with it. You could even go on arduino.cc take a project they made and recreate it , simplest being 'Line follower'.