Q1: When linking with one of my Digimon that has a {{WhenLinking}} effect, this card's Your Turn effect activated before that card's {{WhenLinking}} effect, and I app fused that Digimon. Can I then activate the linked card's {{WhenLinking}} effect?
No, you can't activate it. When a card with an effect that's pending activation leaves its current area while activation is pending, the effect can no longer be activated. In this case, the {{WhenLinking}} effect on the linked card triggers upon the link, but it becomes a digivolution card before the effect can activate and is no longer considered a link card, therefore the effect can't activate.
Haru Shinkai BT21-084 R App Driver/Appmon/Hero [Start of Your Turn] If you have 2 or less memory, set it to 3. [Your Turn] When your Digimon get linked, by suspending this Tamer, <Draw 1>. Then, 1 of your Digimon may app fuse into a Digimon card in the hand. --- [Security] Play this card without paying the cost.
Haru Shinkai BT21-084 R App Driver/Appmon/Hero [Start of Your Turn] If you have 2 or less memory, set it to 3. [Your Turn] When your Digimon get linked, by suspending this Tamer, <Draw 1>. Then, 1 of your Digimon may app fuse into a Digimon card in the hand. --- [Security] Play this card without paying the cost.
Haru Shinkai BT21-084 R App Driver/Appmon/Hero [Start of Your Turn] If you have 2 or less memory, set it to 3. [Your Turn] When your Digimon get linked, by suspending this Tamer, <Draw 1>. Then, 1 of your Digimon may app fuse into a Digimon card in the hand. ---