You can either start from the sample code and gradually modify it and add your own code to it;

or you can start from scratch, that's up to you, but both approaches are possible

But somebody told, don't use sample code. You can create your own code. That's why i got confuse

Well, you can start with it and just add or change the code that is necessary to your application.

Shall i use the same cloud Recog code for my own app?

Thanks for clarifying. Then, of course, the Cloud Reco sample would be your starting point.

sorry for bad english. I don't want Image Targets. I need to use cloud recognition. I stored some images in database, then image recognize i need to retrieved data at runtime using cloud recognition. Shall i use sample code for my own app? Can i customize this code for my requirement?

 the Image Targets sample would then be an excellent starting point.

I have a final idea of my app. I need to use image recognition for my app. When image is matched i need to render some information. Shall i use sample code for my app?

How to customize sample code for my own app ?

That's a very generic question; as a general rule, you will need to study the Vuforia API and the sample code, undesrtand what the sample code does, and then elaborate your own customizations.

Also, before starting any customization, it is generally good to have a clear idea of what are the requirements of your final application.