Sir can I do mechanical engineering after 2year gap of 12th from a medicore private institute will it affect my placement ,should I do this?

Yes, you should definitely go for it. Higher education is very important in order to stand out.

Pursuing Mechanical engineering is after a 2-year gap is slightly difficult but not important. Most engineering colleges require the student to pass an entrance exam, depending on the college. Some colleges accept the result from a common entrance exam (CET/JEE) while others prefer to conduct their own. The validity for these exams is usually one year. Meaning you have to take admission in a college within one year of passing or you will have to appear for the exam again. However, there is also a Management quota that allows a candidate to get admission, sometimes on the percentage of marks scored in the board exam. But this is very rare and normally is accompanied by hefty donations. I suggest you try and clear the entrance exam.

Placements are trickier. Even though they consider the year of passing since your twelfth standard, it really depends on the company an more importantly your performance in the engineering years. Doing additional courses and internships and projects can drastically tip the chances of getting selected in your favor. You will understand more about in as you go through the four years of engineering.

Hope you question was answered to your expectation. Good luck.