For the Mana gain (as posted by kishinmak on the GFaqs boards):
|Formation||Summoned Monster did not act||Standby Monster did not act|
|Any 3x2 Formation||Mana +2||Mana +1|
|Separate Formation||Mana +4||Mana +2|
Ending the turn:Edit
Death. All monsters will have to suffer it eventually. And depending on if you were lucky against your opponent's setup, or had the bad luck to be counter-picked (meaning that the opponent happens to have exactly the right factors to break your setup), different events will take place.
When a monster takes lethal damage (or dies in any number of grisly ways), it is removed from play.
Whatever was the monster's mana cost is then added to your mana pool.
If there is another monster beneath it, that monster will be brought into play. If it has a Reverse effect, and if you have the appropiate mana to pay for it's cost, that Reverse effect will trigger.
The same will happen to your opponent's side (in the case that any of their monsters also died).
It has been my observation, that usually your monster's Reverse effects will take place before your opponent's (in the case of a CPU battle).
Beginning a new turn:Edit
Any additional Mana points are figured in, of those monsters that did not perform any actions the previous turn. Bear in mind, that this happens after any monster's death or Reverse effect (of course, any monster's Reverse effect that adds more Mana to your mana pool will be figured in, but that's still counted as the previous turn).
If any monsters dies, the fighting pauses so that you (or your opponent, if their monster died) may select a new monster to summon. If your monster survived the previous round (or your opponent's) that monster will still be the fighting monster. Again, if you choose to have another monster fight for you, it can only be done if you swap, or your current monster dies. There are effects that can force your monster to be swapped (to the best of my knowledge this is the only time outside of death and swapping, that a monster can be switched).
And from here on, the process repeats itself, until the conclusion of the current turn, and the beginning of a new one.