Confused about what I can and can't do with the Facebook plugin on Android

Can I post on to a friends wall that does not have the app installed? Does my app need to be reviewed by facebook to do this? How do I do this? 

What is the difference between

 facebook.showDialog() 

and

 facebook.request( "me/feed", "POST", { message="Hello Facebook" } ) ?

I heard “feed” will be deprecated and be replaced by “share” for “facebook.showDialog()” is this also true for the above facebook.request()? 

What are ways to invite nonusers to play my game? I know I can do the following

 local params = { app\_id = fbAppID, message = "Try this game!" } facebook.showDialog("apprequests", params)

But how will the recipient try my game if I can’t send a download link with this?

So I tried this code but it didnt do anything. I sent an apprequest to myself but it wasnt there so this doesnt work for some reason.

 local params = { app\_id = fbAppID, message = "Try this game!" } facebook.showDialog("apprequests", params)

Also I tried to post to a friends wall but could not managed to do it. I tried the following but nothing happens when run it.

facebook.request( "friends/feed", "POST", { message = "Great app check it out!", href = "https://play.google.com/store/apps/details?id=com.mygame.app" } ) end

Any idea why?

So I tried this code but it didnt do anything. I sent an apprequest to myself but it wasnt there so this doesnt work for some reason.

 local params = { app\_id = fbAppID, message = "Try this game!" } facebook.showDialog("apprequests", params)

Also I tried to post to a friends wall but could not managed to do it. I tried the following but nothing happens when run it.

facebook.request( "friends/feed", "POST", { message = "Great app check it out!", href = "https://play.google.com/store/apps/details?id=com.mygame.app" } ) end

Any idea why?