Can someone please tell about ISP spying in India?

• Like how far they can legally collect data? And illegally collect data?
• How, and what data they collect?
• How long does they store the logs?
• What are the privacy practices to prevent these ISP spying?

I'm a beginner, and I am looking to self host mostly everything.

Like, what I planned for so long is to, get a rpi4 b+ or le potato, and connect it to a 5 TB hard disk (initially) and dump all my data into it, and degoogle (because I'm not in any proprietary platforms). I wish to have it as my personal server, which I can Access from anywhere. And put upload and download data. And expand it whenever required. I also want to self-host my lemmy and invidious instances (from seperate setup like this). Is this what you all call self-hosting? Or it's too basic and there are lot more advanced stuff that I'm unaware of? Also how to start? Where to start? Is there any guide for a beginner like me?

Which OS has the steep learning curve and is considered hardest?

• Gentoo ( I have been using it for 3 years now, until I have to switch to Ubuntu for research sake. I love it's philosophy and I kinda feel even my lifestyle changed after Gentoo. Tried it's successors, redstar, cosmic mod didn't liked much.)
• Arch Linux ( when I got into Linux, everyone was like, I use arch btw. So tried it first with gnome, then kde, then i3, then i3 gaps and tui, then used openrc, then used runit. Helped me lot to install Gentoo. But Gentoo transformed me into something else)
• Nix OS ( I was hearing about it since 2022. I wanted to try, and now I am gonna install and use it. I'm planning)

My question is, which among these is considered to be hardest and thus by mastering it, one can master linux to atleast some part? (excluding network management, ofsec, netsec, forensics, etc)