Will you please tell me the names of various competitive exams after B.Tech??

Here I am suggesting you the names of various competitive exams after B.Tech, you can appear in one of these after completing the engineering:

All India Services
Indian Administrative Service
India Foreign Service
Indian Police Service

Group A Services
Indian P & T Accounts & Finance Service
Indian Audit and Accounts Service
Indian Revenue Service (Customs and Central Excise)
Indian Defence Accounts Service
Indian Revenue Service (I.T.)
Indian Ordnance Factories Service (Assistant Works Manager, Administration)
Indian Postal Service
Indian Civil Accounts Service
Indian Railway Traffic Service
Indian Railway Accounts Service
Indian Railway Personnel Service
Post of Assistant Security Commissioner in Railway Protection Force
Indian Defence Estates Service
Indian Information Service (Junior Grade)
Indian Trade Service, Group 'A' (Gr. III)
Indian Corporate Law Service

Group - B Services
Armed Forces Headquarters Civil Service (Section Officer's Grade)
Delhi, Andaman & Nicobar Islands, Lakshadweep, Daman & Diu and Dadra & Nagar Haveli Civil Service
Delhi, Andaman & Nicobar Islands, Lakshadweep, Daman & Diu and Dadra & Nagar Haveli Police Service
Pondicherry Civil Service
Pondicherry Police Service