BT26-102 Seven Code PAD

You can place them from your Digimon in the battle area, your Digimon's link cards, or cards in your trash.Additionally, you can choose a total of 6 cards from any or all of these areas. For example, 1 from your Digimon in the battle area, 2 from link cards, and 3 from your trash.

No, you can't. A "by" condition can't be met if only some of the required actions are performed. The conditions for this [Main] effect require you to place 6 of the specified cards as digivolution cards.

Yes, you can.

Yes.