CBSE 12th

Dear Manish,
Well, you can learn in multiple ways, some people learn everything online while some join programs and courses to become a data scientist. I think one needs to cover a certain topics online while certain topics can only be learnt in classroom training module.
Python Basics, Intermediate and Advanced statistics, Probability and Linear Algebra, Linear Regression, Time Series and Cost Function, Types of Data & Exploratory Data Analysis, Collecting, extracting, querying, cleaning, and aggregating data for analysis, Data Sources, Cleaning and Wrangling, Working with APIs and Web Scraping.
These will help you learn the advanced topics of data Science faster and in depth. I would always recommend data Science aspirants to go for a programme which is classroom-based, instructor-led and heavily practice driven. You will come across a lot of institutions, courses, programs that will help you learn data Science. Some are way expensive while some are reasonable. But, one very important thing to keep in mind while you are enrolling for such courses is to know the worth of it in terms of knowledge and what at the end of the course you are developing within yourself. Remember: "80% practical & 20% theory".
Hope this helps.