Diploma

You can't get admission in NIT through lateral entry because they take students only via JEE Mains.

Yes, if you have diploma in civil engineering you can surely get lateral entry in B.Tech architecture but some colleges has some colleges on their own rules. Most universities usually take the lateral entry for civil engineers to the B.Tech architecture you can surely search for that.

Yes, you can surely get the lateral entry to the second year of B.Tech if you have diploma in electronics engineering. There are various colleges which provide lateral entry to the diploma students.

You can surely take admission in 2nd year of B.Tech.

Your diploma percentage is quite low because most of the colleges and Universities want 60% marks students in the lateral entry. Moreover, there colleges which I can suggest for you, you can call of them or email them but do that first because the admission time is about to end up. Firstly, you can try out Vivekananda Global University Jaipur website is vgu.ac.in and secondly you can try Lovely Professional University in Jalandhar and website is lpu.in.

Hello Esh,
GMAT is after graduation and before admission for MBA. 1-year Diploma is independent of it. Also it's good to know your dream of studying in US or Canada. But these are really specialised issues and there are many nuances. I would therefore advise you to go to agency providing these services in your town.

Hello Krishna,
You can do mechanical engineering but your brother suggest you specialization. You can go in any specialization in mechanical engineering.

Yes, I think you can take admission in the nearest college after completing your Diploma from another college in the same branch.