In Yu-Gi-Oh: if I use a spell card that places all face-up attack monsters on the field into defense position.

Question

Could I switch it back to attack and attack my opponent since it is still my turn or does act as if i myself placed them into that position giving up my chance to attack that turn?

Answer 1

Usually you CANNOT switch back to attack position but it depends on the card text of the card you used.

READ THE CARD TEXT EFFECT CAREFULLY. IF IT SAYS 'for the rest of the turn' OR SOMETHING SIMILAR TO THAT YOU cannot CHANGE THE MODE OF THE CARD AGAIN UNTIL YOUR NEXT TURN.

Answer 2

You CAN change the battle position of a monster "manually" if its battle position was changed by a card effect previously that turn, but there are 3 exceptions that prevent you from "manually" changing a monster’s battle position:

Exception #1: You cannot "manually" change the battle position of a monster if it declared an attack that turn (even if the attack was negated or a replay occurred).

Exception #2: You cannot "manually" change the battle position of a monster if it was Summoned or Set that turn by the turn player.

Exception #3: You cannot "manually" change the battle position of a monster if its battle position was already changed "manually" that turn (including if it was Flip Summoned).

Manually: you do the action, not a card effect.