What to do after 12 to be a software engineer?
You want to become a Software Engineer. So you have two paths to choose this diverse and lucrative career.
1. B.Tech - Yes, it's the most usual and common path for Software Engineer. Myself being a follower of this path, can assure you that it is the best one. You will learn coding, networking, database, AI etc during your 4 years of engineering. Do some internships and projects on latest tech to get a good job after completing your B.Tech.
2. BCA + MCA - I know, it sounds quite lengthy. But it actually worth the time you spend. It can consume your 5-6 years. But, I have personally experienced that MCA's have better knowledge and deep understanding of Computer than many B.Tech guys.
Both, the path are very good. If you are strong in Mathematics and analytical reasoning go for B.Tech. Otherwise, choose BCA+MCA.
All the best !!