I have a few friends from University of Allahabad and according to them, the faculty at Allahabad University is amazing. Moreover, the Maths department is the biggest department in Allahabad University. The teachers are well-experienced and cooperative.
The faculty at Allahabad University is not only famous for Maths but also for Chemistry. And due to this reason, every year you get to see at least 2 to 3 students clear in research exams and further get selected in IITs for research.
You can consider University of Allahabad as a valid option for your B.Sc in Mathematics.