hi,

see you may apply for abroad colleges for degree course after completing 12th, however as per course wise eligibility criteria differs and the same thing is for admission process. After completing any degree course in India you may apply for post graduate course in abroad university , so its not like that only after completing engineering course you may go for abroad to study, so you may apply for abroad university after completing any degree courses.

so now you have to decide which course you want to pursue after 12th.

I recommend to do go for masters course in abroad rather than degree course, since the scholarship opportunities are higher for masters student.