Android

Hello Anshuman,If you are really interested in technology, you can do courses like artificial intelligence, internet of things, virtual reality etc. From popular online courses portals like NPTEL, Udemy, Coursera, etc. There are many applications of these domains related to biology also. For example, Virtual Reality domain is widely applied in medicine, especially in surgical training, pain management, treatment for psychological diseases, rehabilitation, etc. And similarly, there are plenty of courses available for learning how to make blogs, videos. You can also start your own YouTube channel, to learn everything from making blogs to video editing. Best wishes.

Hadoop and Android are two very different things. Programming on Android is considered for application programming whereas programming on Hadoop is considered to be system programming. Hadoop comes under category of distributed operating system so if you are interested in making distributed operating system then you are welcome to use Hadoop but I would suggest you to go from the basic of distributed OS. Application programming is much easier as it focuses on "Looks" and various functionality that you want to provide, whereas system programming is back-end on server side and it is completely hidden from the user and it is very much difficult as you have to manage servers, database, fault-torrent systems, real-time operating systems etc. And all of them are really tough and you need great skills to in both theoretical knowledge and practical programming skills. Also, youu2019re in designing of algorithms, understanding/modifying existing code plays crucial role as well. If you are interested in system programming then it is good thing but you will have to be very good in it. One small mistake and you will destroy all user data which will surely end your career.

As far as Android is concerned, it has a very awesome future ahead. Everything is going to mobile these days, from shopping your clothes, booking movie ticket, booking railway ticket to order vegetables to doorstep and there are lots of things needed to move to mobile now.
Most of android developer work for companies in India, some of them are working as freelancers and very few are working on their own idea. If you have a great idea that can change the way of anything (Like WhatsApp took the text chat on another level, it is so easy to use that everybody wants it first on their smartphone).
In India so many companies are hiring android developer (almost 6 of 10) and startups are offering really handsome packages to a smart developer.
If you have good hands on java then it is so easy to learn android development.