When 'Banner of Courage' activates does its effect continue to increase attack during every battle phase?

Answer 1

The +200 ATK bonus is applied only 'during your battle phase', this is a continuous effect that does not use the chain. As soon as the battle phase ends, the +200ATK ceases to apply, but will be reapplied during your next battle phase.

So say you have a monster with 1700 attack, it will ONLY have 1900 (+200) attack when you're in your battle phase and when you're back in your main phase 2 or end phase it goes back down to 1700 (-200). One thing to note is that you'll get the +200 attack during BOTH your own battle phase AND ALSO your opponent's battle phase.