Monsters can only 'manually' change battle position in your main phases. If you want to change them during the battle phase, you will have to do it by a card effect.
Chat with our AI personalities
Yes, that is allowed. You cannot, however, attack and then change to defense in the same turn.
Yes. The 'cannot change battle position' limitation is only for manual changes such as flip summons or putting a monster into attack mode. The monster's position can still freely be changed by effects.
A monster in face-down Attack position is unable to declare attacks. It can be flipped or Flip Summoned, both actions will switch it into face-up Attack position. It can also have its battle position change by the controlling player, switching it from face-down Attack position to face-down Defence position.
No, a monster cannot manually change battle position on the turn it was special summoned, though it can be changed by an effect.
A monster can't manually change battle position on the turn it declared an attack, but it can still be flipped face-down by an effect. Golem Sentry can attack, then activate its effect in main phase 2 and flip itself face down.