Hey,
There is no age restriction to apply for undergraduate courses.You can begin your graduation at any age all you need is that zeal and passion to study and you will make your way through all the ordeals. However for IITs and Medical entrance exams like NEET there is age limit but for graduation in general courses like Humanities and Science there is no such age limit.
But there are certain prerequisite to apply for the  courses like minimum marks in your 10th and 12th which may vary for different colleges and courses.
So you better go through the admission brochure for the desired course of the college or university before applying for admission.
Hope this helps.
Good luck.