hi,
for diploma in engineering admission you can submit your 10 th marksheet or vocational training marksheet both. however diploma in engineering can be done after 10th or 12th.
in every state there is polytechnic entrance test which you may attempt.
goa polytechnic entrance exam form will be available on the month of may ,2020. you should apply for it.
follow the below link for more details.
https://www.google.com/amp/s/engineering.careers360.com/articles/goa-diploma-admission/amp