Endpoint Protection

I want to apply three Application and Device Control Policy on my Parent Group

Application and Device Control Policy - Block Hosts File Modification
Application and Device Control Policy - USB Block
Application and Device Control Policy - Web Site Block

I have four different groups Laptops, Desktops, Servers and VIP's

I want to apply USB Block on Laptops and Desktops
I want to apply Website Block on Laptops, Desktop, Servers and VIP's
I want to apply Block Hosts File Modifications on Laptops, Desktop, Servers and VIP's

How can i achieve this.

Remove inheritance from each group (You can do it in the policy tab of the corresponding group).Create  policies (In the policy tab of SEPM i,e in left side under corresponding policy type).Assign to required groups. 

Small clarification.
Can you tell me how you are blocking web sites with  Application and Device Control Policy .I had never seen a doc for it I am not getting the idea also.can you point it tome? Or you are going to block browsers?

By default all the groups are under parent group so it inherits the policy from Parent group. If u want to deploy different policy to different groups then Uncheck the Policy inheritance from Clients-->Select Group-->Click Policy in right side column and uncheck it. After unchecking the policy inheritance u will be able to apply the policy to desired groups

u Can visit these links for more knowledge

https://www-secure.symantec.com/connect/forums/policy-implementations

Shared and Non-sahred po.licies

http://seer.entsupport.symantec.com/docs/330856.htm

Your first link refers to same thread.