Heidelberg University (Germany)

I'd like to congratulate you. You are already ahead of many of your competitors by starting in 12th. A few things you should know beforehand –
The competition is VERY high. You have to be in the top 99.5 percentile to get into a government college. If you're like most people, you wouldn't want to take a drop, so I'd suggest that you keep a backup plan. Prepare well for boards too. You should start off by knowing about the exam and it's marking scheme first. 180 questions, +4 for every right answer, -1 for every wrong answer.
Total marks: 720. You should aim for 600+. It has 45 questions of physics and chemistry each, and 90 questions of biology. For biology, you have to master NCERT. You should literally know every line of the 11th and 12th biology NCERT by heart. Once you have done that, you can move on to your coaching books and notes. Aim for 320+ marks in biology. Chemistry
Physical and organic chemistry is all about knowing the concepts and solving as many MCQ's as you can. Reading only NCERT will not do. Inorganic chemistry can be studied directly from NCERT, no need to cram any high level coaching stuff. Aim for 150+ marks in chemistry. Physics is the subject which differentiates between the good and the exceptional student. Devote atleast 40% of your time to physics. It will help if you have taken maths as your 5th subject. If not, you should get a tutor to teach you basic calculus which will come in handy for physics. I personally suggest that you solve HC Verma. It's a tough book, I know, but it builds a strong base. You can solve your MCQ's with ease after you've done HCV. Aim for 140+ marks in physics. I will also advice you to take some form of coaching. If not classroom coaching, you can take a distance learning programme. You could also purchase an Aakash Itutor. The coaching you will take will also provide you with regular tests, which will tell you where you stand, so you can modify your studying strategies accordingly.

Yes, you can sit on counselling of two different states for BE and B.Tech admission. Preparing for an entrance exam like JEE Main or for that matter MHT CET or KEAM is no walk in the park. But, even if one crosses this hurdle with relative comfort, there are more down the lane that are almost like a web. Here we are talking about the complex admission processes weaved across different states. Take for example, the B.Tech admission process for other state candidates in Himachal, where you get 15% reservation for all India candidates; admission is first based on JEE Main rank, followed by merit in HPCET. Now if you move to Tamil Nadu, there is not much of a quota for all India candidates, but a limited 50 seats offered by Anna University, with admission based on 10+2 scores. Now, if you didn't know this subtle difference, you might spend fruitless time seeking admission to an institute in Tamil Nadu, based on your JEE Main score (if you had one), when you might have been better off applying for admission in Himachal. To ensure that no such thing happens and you maximize your chances, we urge you read up on the topic B.Tech admission for other state candidate. It will equip you with the correct and pertinent information, and make your life a lot easier.
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https://www.shiksha.com
All the best.
Thank you.