Hi Aspirant,

There's no certain age or course restriction for learning computer science. There may not be availability of full time course(except for a very few diploma courses) for learners from commerce background but you can start off with learning basics of coding, data structures and algorithms, networking, etc. As a beginner, you can start with c programming  language, understand the logics of each code you are creating, practice it more and more, create projects in c. Only after that learn other programming language. Now as you would have learnt a few basics of computer programming, you can start competitive programming on platforms like Codechef, Hackerank,etc. There are a lots of companies who hire professionals through such platforms.

Now to learn programming, data structures, algorithms, networking and then advance things like Artificial Intelligence and Internet Of Things,etc , You can use a lot of online platforms and tutorials.

At the same time you can refer books below which are purely for beginners,

1)The C Programming Language written by Dennis Ritchie and Brian W. Kernighan

2)Let us C by Yashavant Kanetkar

3)Data Structures and Algorithms Made Easy: Data Structures and Algorithmic Puzzles by Narasimha Karumanchi.

Also please learn some basics of Descrete Mathematics which will be helpful for learning Data Structures and Algorithm.

Hope this is resourceful.

Good luck!!!