What facebook permissions do I need?

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C#

Facebook-API

Hi,

I am trying to learn to create Facebook apps, so I created an App in Facebook Developer. I got the Applicaton ID and Secret. And then I got stumped on the permissions.
I understand that the users will see a list of the permissions requested by my app when they login to it, but how are they used? To be precise -

1. What permissions will my app require to post a status, like a page, reply to a post and such? Where can I find an exhaustive list of permissions and their usage/definition etc.?

2. Do I need to enter the permissions in the Facebook Developer app dashboard (under permissions tab) or do I need to define them in the URL (e.g: "http://www.facebook.com/dialog/oauth?client_id=APP_ID&scope=COMMA_DELIMITED_LIST_OF_REQUIRED_PERMISISONS&redirect_uri=SOME_URI&response_type=token")

3. Can I change these permissions at a later date?

Thanks.