Sorry to inform you that you can’t write IAS or IPS exam after completing Diploma. The eligibility for IAS/IPS exam is to be a graduate from any recognised university. As diploma can’t be treated equal to degree so you have to complete your degree course and after that you can apply for IAS/IPS Exam

Eligibility Criteria for UPSC IAS /IPS EXAMS:

Educational Qualifications:
Must have ---
Bachelor’s degree of a recognized university with at least one of the subjects namely Animal Husbandry & Veterinary Science, Botany, Chemistry, Geology, Mathematics, Physics, Statistics and Zoology
Or
Bachelor's degree in Agriculture, Forestry or in Engineering or an equivalent qualification.

Age limit:
21 years must be completed on 1st August of the year, which a candidate is appearing.
Maximum 30 for general category, 33 for OBCs and 35 for SCs/STs.