Can you play a hidden card from the facedown zone on your own turn?

Ruling: Yes, you can play a card from the facedown zone during your turn at reaction speed whenever you have priority, as long as it wasn't hidden there during that same turn.

Sequence:

• You cannot play a hidden card immediately at the start of your turn if there are no triggers during the beginning phase
• You must complete Channel and Draw (ABCD) first
• After ABCD is complete, you can play from the facedown zone whenever you have priority
• You cannot play it during a showdown or if there's an existing chain where your opponent has priority

Nuances:

• Your opponent can respond if the card is a spell or has a "When You Play Me" trigger