Q1: Can I use this card's When Digivolving When Attacking effect to link a card that doesn't have {{Link|}}?
No, you can't.
Lv.6 Gaiamon BT21-101 SEC God/Appmon | God | Creation [App Fusion] [Globemon] & [Charismon]: Cost 0 (If 2 such cards are linked together, stack the link card on top and digivolve.) <Blocker> <Link +1> (Add 1 to this Digimon's maximum links.) [When Digivolving] [When Attacking] You may link 1 Digimon card with the [Appmon] trait from your hand or this Digimon's digivolution cards to 1 of your Digimon without paying the cost. [Your Turn] [Once Per Turn] When your Digimon get linked, by unsuspending this Digimon, trash your opponent's top security card.
Lv.6 Gaiamon BT21-101 SEC God/Appmon | God | Creation [App Fusion] [Globemon] & [Charismon]: Cost 0 (If 2 such cards are linked together, stack the link card on top and digivolve.) <Blocker> <Link +1> (Add 1 to this Digimon's maximum links.) [When Digivolving] [When Attacking] You may link 1 Digimon card with the [Appmon] trait from your hand or this Digimon's digivolution cards to 1 of your Digimon without paying the cost. [Your Turn] [Once Per Turn] When your Digimon get linked, by unsuspending this Digimon, trash your opponent's top security card.
Lv.6 Gaiamon BT21-101 SR God | God | Creation (App Name) {{AppFusion|0|Globemon|Charismon}} <Blocker> {{Link+1}}. [When Digivolving] [When Attacking] You may link 1 Digimon card with the [Appmon] trait from your hand or this Digimon's digivolution cards to 1 of your Digimon without paying the cost. [Your Turn] {{OncePerTurn}} When your Digimon get linked, by unsuspending this Digimon, trash your opponent's top security card.