do the caste certificate need to be exactly same as given by josaa or there is some flexiblity

Hello!
Yes, caste certificate should be exactly in the same format as provided by josaa actually to avoid any kind of ambiguity they ask for the same format.
To get away with any kind of problems, one should provide the same format of caste certificate as provided by JOSAA.
So don't give a change of not getting selected because of the different format of caste certificate.

Providing the link to get more details, kindly visit:-
http://www.engineering.careers360.com/articles/josaa-counselling

Good luck:)