How to detect whether the ios app is pirated or not? This is my first question here and iOS is something very new for me currently.
If we have an app on iTunes and same app on some third party appstore, then does it mean the app is pirated ? 

How to detect if an app on Third Party Store is pirated version of the original app from iTunes ?
Any help is highly appreciable. 

Thanks in advance.
You can only install apps from itunes/the build in app-store.
Some apps are/claim to be installable through safari, but I wouldn't trust that.
If you have jailbroken your phone and installed an alternative app store, that is probably illegal, and will void your warranty (because apple won't let you jailbreak).
So if you have found a third party app store, it is probably fake, or illegal.