B.Tech Eligibility

You can follow the link:
http://www.samundra.com/html/Applications/CombinedDNSandGMEApplication/application_Btech.html and apply online.

Yes, you can. Many countries and colleges will allow you to apply for B.Tech, but some colleges will allow you to apply for advanced diplomas or so. So, you should start checking college's websites for the requirements and email them also.

Yes, you can pursue B.Tech in mechanical engineering. You need to appear for the lateral entry entrance exam.

Australia is awesome in terms of education, and duration is 3 years rather than 4 years. To gain entry into an Australian undergraduate course, you need to have class 12th passing certificate. Almost all programmes require a score of IELTS exam, which must not have been taken 24 months before the day of the application and should be more recent. Students should have a minimum IELTS score of 6 and at least 60 in class 12th board exam. Scholarships are available to Indian students.