You can take any number of times & There is no age limit
Bachelor degree holders in Engineering/Technology/Architecture (4 years after 10+2) and those who are in the final or pre-final year of such program.
Master degree holders in any branch of Science/Mathematics/Statistics/Computer Applications or equivalent and those who are in the final or pre-final year.
Candidates in 2nd or higher year of 4-year Integrated Master degree program
(Post-B.Sc.)or in 3rd or higher year of 5-year Integrated Master degree program and Dual Degree program in Engineering/Technology.
Candidates with qualifications obtained through examinations conducted by professional societies recognised by UPSC/AICTE (e.g. AMIE by IE(I), AMICE(I) by Institute of Civil Engineers (India)-ICE(I)) as equivalent to B.E./B.Tech. Those who have completed section A or equivalent of such professional courses .
http://www.successcds.net/engineeringentranceexam/GATE/Graduate-Aptitude-Test-in-Engineering.htm
Bachelor degree holders in Engineering/Technology/Architecture (4 years after 10+2) and those who are in the final or pre-final year of such program.
Master degree holders in any branch of Science/Mathematics/Statistics/Computer Applications or equivalent and those who are in the final or pre-final year.
Candidates in 2nd or higher year of 4-year Integrated Master degree program
(Post-B.Sc.)or in 3rd or higher year of 5-year Integrated Master degree program and Dual Degree program in Engineering/Technology.
Candidates with qualifications obtained through examinations conducted by professional societies recognised by UPSC/AICTE (e.g. AMIE by IE(I), AMICE(I) by Institute of Civil Engineers (India)-ICE(I)) as equivalent to B.E./B.Tech. Those who have completed section A or equivalent of such professional courses .
http://www.successcds.net/engineeringentranceexam/GATE/Graduate-Aptitude-Test-in-Engineering.htm