I want to use some of the APIs provided by Firefox OS. But many APIs are accessible only for privileged and certified apps. Firefox OS documentation suggests (as far as i understood) that "the apps which are deployed in marketplace are privileged apps". But how can i deploy an incomplete app to the marketplace without even testing the functionality of those APIs? Is there any other way to access those APIs? Thanks in advance
You can test your app using the FirefoxOS Simulator: https://developer.mozilla.org/en-US/docs/Tools/Firefox_OS_Simulator
Depending on the APIs you're testing the simulator can help. Some aren't available due to hardware not being available on a desktop device.
Also, if you are developing a "hosted app", you have access to APIs which use web permissions. If you need more than that you would need to create a "packaged app" with type=privileged and specify which permissions you want access to in your manifest. This is described here: https://marketplace.firefox.com/developers/docs/packaged
The app permissions table will tell you if the APIs you want required hosted, packaged, or certified (only available shipped on device).