I am reffering group B here....12th GSEB 2019 board exam

My query is - am I eligible for supplymetory exam by july 2019 for three subject i.e. physics, chemistry and Biology...

Another query is - if I wish go for engineering field then how do I go for that as I am in Group B 12th standard..

As far as your supplementary exams are concerned, it will be better to go and take help of your school adminisration. usually if you fail in more than one subject, you have to repeat.talking about B.Tech, mathematics is compulsory for it. so if you are repeating the year, you can change your subject from biology to maths but remember that it will be extremely difficult to cope up with it.other options are doing a polytechnic course or engineering diploma.