Still I am not able to understand the difference clearly.
1. The difference is difficult to understand, and many people never fully understand it.
2. The difference is not difficult to understand, but some people don't fully understand it.
3. Although the difference is not difficult to understand, some people don't fully understand it.
4. Even though the difference is very simple, some people don't fully understand it
#1: and - What is said in the second clause is a natural thing to say in light of what has been said in the first.
#2: but - There is a contrast here. After what has been said in the first clause, the second is (slightly) unexpected.
#3: although - Very similar to #2. Although is perhaps a little more formal than but.
#4: even though - a much stronger contrast. The speaker is surprised or exasperated.
The difference is clearer in: Although Jones wasn't the obvious choice for the job, I thought he had potential, and so I appointed him. Even though Jones was not at all the sort of person I wanted, there were no other candidates, and so I had to appoint him.
ps. It isn't a good idea to address your questions to just one person. You might put off other people who could give an answer that might be just as good - or even better.