Question: I want to develop a WordPress theme similar to another theme present on the internet. Shall I use the default WordPress theme to start from or start from scratch? 

Please guide me.

Answer: 
Go with WordPress TwentyFifteen or any other default theme. 

You don't have re-invent the wheel, you will save a lot of time.
For learning & understanding I think you should start from [wordpress blank theme](https://wordpress.org/themes/blankslate/)