GATE

Dear Student,
There is no age limit to appear in GATE exam. For the eligibility related to qualification you need to check this link
http://www.gate.iitr.ernet.in/?page_id=266
All the best.

GATE has three benefits:
1. Entry to PSUs.
2. Entry to top level institutes for M.Tech.
3. Scholarship of 12000 per month, if you take admission in Government College for M.Tech.
But, your GATE score must be good to get any of the above.

GATE aspirants follow different strategies for success, but there is no magic formula guaranteeing GATE exam success. Experts agree that only hard work, planning and starting early, will maximize the chances of success.
A recognizable score in GATE offers a kick start to the career of the student. GATE exam happens in the month of February, i.e. during the last semester (8th) of engineering. Hence, a student will have only six month, if he starts preparing in the 4th year of engineering. Most students are baffled as to when they should start preparing for GATE exam. Experts says that 3rd year is the best time to start GATE preparation.

The notes are available of Made Easy for different branches in market. You can ask for the subscription of books by Career Launcher. Apart from these, you can read your subject reference books.
Quantitative:
1. Arun Sharma, Publisher: Tata McGraw Hill,
2. Pearson Guide to Quantitative Aptitude and Data Interpretation for the CAT by Nishit Sinha.
3. Quantitative Aptitude Common Admission Test by Sarvesh K Verma.
4. Data Interpretation and verbal: Arun Sharma - Tata McGraw Hill.
5. Pearson Guide by Nishit K. Sinha.

When you are in the pre-final year or final year of graduation, you can start preparing for GATE. 6-7 months of dedicated preparation is enough to get a good score in GATE exam.

Hi,
As per the details mentioned on the GATE official website, they have not mentioned whether they do not accept distance learning Bachelor's degree for particular domain, in which you want to apply for GATE exam.
All the best.