Can I do a BTech in computer science from IGNOU?

In this era, if you want to engage in computer science, you don't need a degree. Unfortunately, the Indian system values degrees as well as relevant skills. All you need is a good computer, an internet connection, and a desire to learn. If you cannot afford four years or a large tuition fee for engineering, consider taking some related courses such as mathematics, statistics, or commerce.

You can learn skills on your own using free and paid online platforms, complete projects related to your skill set, and you'll be employable, possibly better than an engineering graduate.

Practicals (Lab sessions) are regarded as the backbone of engineering courses in other branches (though our colleges give much more importance to theory). 

Many prestigious institutes outside of India are focusing on "outcome-based education." That is, simply having the certificate and having no idea what you did in college, or simply studying for the sake of passing the exam, isn't a big deal. You must be an authority in your field.