Camera2api

There are 2 reasons aa far as i can think, 1. Opening Camera2Api control to 3rd party apps will risk the Camera hardware, 2. If they are unlocked people will most probably use Google Camera rather than SAMSUNG Camera, Which samsung clearly doesn't want. SAMSUNG is trying their best to make people use their services instead of Google services.
For example See Samsung Internet, Samsung Gallery, Samsung Notes, Samsung Drive (One drive), etc etc.

Ab kuch game samajh aayi Samu ki?

If my answers resolve your query please Accept it as solution.

You can't. This can be done by only software update and samsung is not going to do that. Cause they have to push higher A series phones with premium features & performance whereas M series with mid performance and limited features with big batteries.