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?