I just wanted to know how I could get every single tweet "tweeted" by the user by using MGTwitterEngine.
You want to look at:
getUserTimelineFor:(NSString *)username sinceID:(MGTwitterEngineID)sinceID startingAtPage:(int)pageNum count:(int)count
set sinceID=0
but twitter has limits on what it will return so check the docs here: http://dev.twitter.com/doc/get/statuses/user_timeline