Q1: Can I use this card's End of Your Turn effect to place this Tamer and 1 Growlmon and 1 WarGrowlmon from my trash as the bottom digivolution cards of 1 of my Guilmon, but choose to not may digivolve into Gallantmon?
Yes, you can. The effect reads "may digivolve," so you can choose whether or not to digivolve.
Q2: If the Gallantmon digivolved by this card's End of Your Turn effect has Blitz, can I activate it?
Blitz can activate as long as your opponent has 1 or more memory when you would activate the effect.
Takato Matsuki BT17-080 R [Start of Your Main Phase] If you have a Digimon with [Guilmon], [Growlmon] or [Gallantmon] in its name, gain 1 memory. [End of Your Turn] By placing this Tamer and 1 [Growlmon] and 1 [WarGrowlmon] from your trash as 1 of your [Guilmon]'s bottom digivolution cards, that Digimon may digivolve into [Gallantmon] in the hand, ignoring its digivolution requirements and without paying the cost. --- [Security] Play this card without paying the cost.
Takato Matsuki BT17-080 R [Start of Your Main Phase] If you have a Digimon with [Guilmon], [Growlmon] or [Gallantmon] in its name, gain 1 memory. [End of Your Turn] By placing this Tamer and 1 [Growlmon] and 1 [WarGrowlmon] from your trash as 1 of your [Guilmon]'s bottom digivolution cards, that Digimon may digivolve into [Gallantmon] in the hand, ignoring its digivolution requirements and without paying the cost. --- [Security] Play this card without paying the cost.
Takato Matsuki BT17-080 R [Start of Your Main Phase] If you have a Digimon with [Guilmon], [Growlmon] or [Gallantmon] in its name, gain 1 memory. [End of Your Turn] By placing this Tamer and 1 [Growlmon] and 1 [WarGrowlmon] from your trash as the bottom digivolution cards of 1 of your [Guilmon], that Digimon may digivolve into [Gallantmon] in the hand, ignoring its digivolution requirements and without paying the cost. --- [Security] Play this card without paying the cost.
松田啓人 BT17-080 R 【自分のメインフェイズ開始時】名称に「ギルモン」/「グラウモン」/「デュークモン」を含む自分のデジモンがいるなら、メモリー+1。 【自分のターン終了時】このテイマーと自分のトラッシュの「グラウモン」と「メガログラウモン」1枚ずつを自分の「ギルモン」1体の進化元の下に置くことで、そのデジモンを手札の「デュークモン」に進化条件を無視してコストを支払わずに進化できる。 --- 【セキュリティ】このカードをコストを支払わずに登場させる。