I posted a few of these over at Gameboadgeek forums, but not all have been answered yet. I figured I would post them all here for anyone else inquiring about such things.
1. Are there starting hand mulligans?
2. Are there sideboards allowed in tournaments?
(Chris Long answered 'No' to both of these questions.)
Here are a couple others that haven't been cleared up...
3. Is there a limit to your hand size?
4. How long of a window do you have to activate a response trigger? End of phase? I ask this, because you can't always immediately activate a response trigger if you don't have priority. So for instance, could i activate a response at the end of the entire turn, even though the requirements were met during the first phase? Or do I only have until the end of the phase that the requirement was met in to trigger the response?