Diploma

Engineering Diploma candidates are eligible to get direct admission in the 2nd year of B.Tech.courses.A candidate who has completed diploma engineering in any stream can get admission in the 2nd year through the lateral entry scheme.The colleges generally take admission on the basis of Diploma marks. But some of the colleges conduct entrance examination LEET(Lateral Entry Entrance Test).
Almost every college reserves some seats for Lateral Entry Scheme.
There are many colleges all over India which give admission on the basis of LES. Good luck.

It will be bad. You can not target a high ranking university as they will see all your scores. Sometimes even from grade 12th. Try to look for a good gre score

Yes but since your score does not seem good enough, don't target a high ranking university. Also appear for GRE n get a good score, that can help. To be safe look for new Zealand, Australia too as these countries are yet not very competitive