There are two ways to become a CEO of software company:

1. Start your own company, basically Startup. In that case, all you need in background knowledge, preferably a CS or ECE degree. And you can decide your own salary.

2. Become a CEO at a software company. That will take years. To become a CEO, you need a managerial degree, that is, MBA. You can have any BTech degree. BTech will help you get job at software firm, give you experience and get you insights how the software world operates. To be able to become a CEO, then you need to have a MBA degree.

Now, if you want to go for IIT. Focus on you studies, focus on clearing JEE Mains with at least 180 or 200 marks and then cracking JEE Advance successfully, under 6000 AIR (for general category). Once you clear that, choose any branch. Preferably, CS, ECE or EE. However, if you don't get any of these, take any branch and get into IIT. There you can switch you domain into Software side, irrespective of your branch. You will be able to get software roles, irrespective of your branch.