Hi,
In general basic of many chapters is used but limit and derivative is most important whereas theory chapters are not even used.

Mathematical reasoning

Hello Tanmay
Well, that's a great a question to ask and this information will help you focus on the chapters which will be useful in class 12th also.
To start with Sets, Realtion and Functions, these chapters are really important as Sets will be used in other chapters too and there are extended chapters of Relation and Functions in class 12.
Next Comes Permutation and combinations, this chapter is not present directly but the concept is very useful in class 12 Probability.
Other than these, do focus on Trigonometric Formulas and Continuity and Differentiability, these will help you a lot in class 12.
Linear Inequalities will help you with Linear Programming in Class 12
Statistics, Complex Numbers and Binomial theorem are of little to no use in Class 12.
Other Chapter in class 12 are new concepts and you don't have to worry about them before hand e.g. 3-Dimensional Geometry, Integration, Inverse Trigonometry. These chapters will be taught to you in class 12 and you don't have to worry about them.
I hope this information Helped you.

Good Luck !!!!