How should I use the 6–7 months before starting a B.Tech in CSE?

Cybersecurity is broad, so you don’t need to choose a specialization immediately. Keep your current Linux and networking practice, but focus on fundamentals such as operating systems, processes, files, permissions, TCP/IP, and basic scripting. A sensible plan would be roughly 70–80% entrance and school preparation, with the remaining time divided between programming practice and a small amount of Linux or networking.

If you still have an entrance exam ahead, make that your top priority. A good rank and strong Class 12 fundamentals will help more immediately than trying to learn several technologies. Alongside your studies, spend a small, consistent amount of time programming—Python or C is fine—and solve basic problems rather than collecting tutorials.

Start by checking the curriculum of the colleges you’re considering and prepare for the subjects that appear early: programming, discrete mathematics, calculus, data structures, and computer organization. Learn one language properly, preferably C or Python, and build two or three small projects. That will give you a much better base than briefly studying web development, cybersecurity, AI, and mobile development all at once.