Hello vaibhav pandit

I hope you are doing good. I would like to tell you that for getting into an army after 10+2 can be done by two options NDA And TES(tecnical entry scheme). As per you query , if you want to btech you can go for technical entry scheme , in which you have to fill the form . After filling the form ,depending on  the number of candidate applied, they shortlisted candidates by deciding a cut off and  then shorlisted candidate have go through only SSB round (most important). All the expenses of education ,training of final selected candidate are done by the army.

I personally advise ypu to go for tes because at your percentage you will easily get a call from them. I am sharing below the link for your reference.

http://www.joinindianarmy.nic.in/writereaddata/Portal/NotificationPDF/TES_44.pdf

Hope you found this answer helpful. Good luck for your future

If you have any other doubt then you can always reach us to clear them :)

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Thankyou