how to get STM32F4Discovery board as a sample. bcoz i am looking for any higher level controller.

 

You usually get samples from the manufacturer or their designated sales reps, distributers etc. But they are usually hoping for some paying business though many may have budgeted for samples. The more expensive their product is the less likely it will be free. Tech businesses also should have budgets for purchasing products they need or want to try because everyone will not hand out free what they have developed. Do some homework about who makes and sells what you are looking for and making your case as to why they should GIVE you something or sell it to you at a discount.

 

The Discovery boards are not that expensive.

US$8.70 for STM32F0DISCOVERY
US$14.58 for STM32F4DISCOVERY

http://www.st.com/web/en/estore/5109fb000cf2b5daeffcff59