But my as its part of my academics, I need to start from scratch that is to learn HDFS and move upwards, so anything that can help me when the situation is like this ?
If you really have to learn how Hadoop works, you'll probably have to look at the source. Write the Hello World program and get it to run on AWS EMR (as others have suggested). Then clone the source to Hadoop and open it in your favorite editor. If you have to understand the nuts and bolts, the source code is the way to go. If you only have to know how to use it, then a book + online tutorial + simple project will get you up to speed within a week or two.