Just want to know which tools and technologies are used to build popular android app like instagram app, facebook app, twitter clients etc? do they use framework like phoneGap or appcelerator or they write native code?
appcelerator is not a webview wrapper like phone gap. It complies down to use native code to generate its app.
I would assume that most large scale companies would invest in having a native app built for all of there solutions.
If this is to judge what you should use the best approach is not to copy what others do but to see what is required for your application and what best suites your skill set