I filled wrong school and board in my jeemains form !..i got 1277 rank..and now i can't change board in mains form ! Can i apply for DTU ?

It should not be a problem. Your name, parents name and 12th roll no should be correct. Since JEE Main is now independent of class 12 board marks, your rank will remain , just ensure you take all the originals documents to the counselling and explain your error in filling up the form.

Please apply for JoSAA also. You should try and see if they consider what is a mistake from your end. Alternately apply for JAC Delhi - which will be for DTU, NSIT and IIIT Delhi. Apply to IIIT Hyderabad also. You have a good rank. I frankly dont know if they will consider for JoSAA but since you will have all the proof, they may consider. So go for that also.