2
The scope related parameters are really provider dependent. You will have to look up the parameters and what is possible up in the documentation of the particular provider (for FB, check here for info on scope: https://developers.facebook.com/docs/reference/dialogs/oauth/).
As for e-mail on Twitter: they simply do not hand over this information. So, your app will have to cope with that.
See:
Source:stackexchange.com