Hi Anmol,
Being sincere and working hard since from day 1 {starting of your 11 std} in the right direction will surely get you succes when you give your exam directly afer 12th.
These 2 years, 11th and 12th are very important. Why simply waste these 2 years and then take a year drop?? Instead work hard from the beginning and try to do it at one go.
Even though you gave your best but things went wrong , only then consider the other option of dropping a year [if needed].
Life is short and uncertain, so try to achieve your goals as soon as possible. One whole year is a lot of time. Simply dont waste it.
ALL THE BEST !!