Am I Eligible for Btech after compartment in 12th??? Which are the entrance examinations for B. tech admission???

You can apply for the B. tech course after completing your backlogs in 12th with minimum 60% and you can have studied mathematics in your 12th.

After completing your backlogs you are eligible for following engineering entrance examination:

JEE Advanced Indian Institutes of Technology Joint Entrance Examination
JEE Main Joint Entrance Examination Main
AIEEE All India Engineering Architecture Entrance Examination
BITSAT Birla Institute of Technology and Science Admission Test
ENAT EPSI National Admission Test
VITEEE Vellore Institute of Technology Engineering Entrance Exam
NAT National Aptitude Test
GATE Graduate Aptitude Test in Engineering
PACET Planning and Architecture Common Entrance Test
ATIT Admission Test for ICFAI Science and Technology
ISAT IIST Admission Test
WAT Written Admission Test
MERI Entrance Exam Marine Engineering & Research Institute Entrance Exam
AMIE Associate Membership of Institution of Engineers
NEAT National Engineering Aptitude Test
NATA National Aptitude Test in Architecture
ECET FDH Engineering Common Entrance Test for Diploma Holders ECET
MHTCET Maharashtra's Common Entrance Test
CET Karnataka's Common Entrance Test
TNEA Tamil Nadu Engineering Admissions
UPSEE Uttar Pradesh State Entrance Exam
COMEDK Consortium of Medical, Engineering and Dental Colleges of Karnataka
EAMCET Engineering, Agriculture and Medicine Common Entrance Test
KEAM Kerala Engineering Architecture Medical Examination
Assam JAT Assam Joint Admission Test
CENTAC JET Pondichery Centralised Admission Committee Joint Entrance Test
Bihar CET Bihar Common Entrance Test
KRLMPCA CET Karnataka Religious & Linguistic Minority Professional Colleges Association Common Entrance Test
BPEE CET Jammu and Kashmir Board of Professional Entrance Examinations Common Entrance Test
Punjab CET Punjab Technical University Combined Entrance Test
Orissa JEE Orissa Joint Entrance Examination
RPET Rajasthan Pre Engineering Test
MP PET Madhya Pradesh Professional examination Test
WB JEE West Bengal Joint Entrance Examinations Board
IPU CET Guru Gobind Singh Indraprastha University Common Entrance Test
CPET Combined Pre-Entrance Test
PJET Puducherry Joint Entrance Test