What are the proper practice in order to understand the subject in a chronological order?
Not saying that this is the best, but it's how I mostly study stuff.
1. Research about the broad topic. (e.g. what is bitcoin)
2. Research about the terminologies I might not understand (e.g. what is decentralization, blockchain, cryptography, etc).
3. Once I get a good grasp on the basic stuff, I then move on the the sort of "supplementary" topics, like the economics of bitcoin and such.
4. Repeat step 2 for the economics of bitcoin, for the technical economics terminologies.
5. etc
6. Read around forums and Reddit and such, and check out some beginner question topics to see if I have enough knowledge to answer most if not all of them in a precise and accurate manner.
Obviously the steps are oversimplified, but you get what I mean.
What are the different approach to make sure that the knowledge is intact in the long run?
It's really common for me to forget stuff especially for the more technical stuff. You could either have some notes on a .txt file, or just simply re-research the stuff you forget.
How do you study the subject in a time efficient manner?
Ehh. I don't like rushing things really, it's not like I'm going to have an exam next week or something. I like taking things slow and steady.
If you like learning faster though, not only concerning bitcoin but learning in general, put your phone away and close all your social media tabs on your browser. Seriously. They take up A LOT of time.
Any opinions or tips?
People are going to have different ways of learning things. What works for me, might not work for you, and vice versa. Just do trial and error and stick with what works best for you.