

Q1: Can I use this card's On Play When Digivolving effect to give Collision and "Start of Your Main Phase This Digimon attacks" to a Digimon that isn't affected by effects?
You can give that effect to such Digimon, but if the Digimon isn't affected by effects upon the trigger timing, the gained effect won't trigger.
Q2: I chose my opponent's BT16-048 TyrantKabuterimon for this card's On Play When Digivolving effect. If BT16-048 TyrantKabuterimon then attacks and is suspended at the start of the main phase, does its gained Collision activate?
No, Collision doesn't activate. As soon as BT16-048 TyrantKabuterimon suspends, its All Turns effect prevents it from being affected by your effects, and Collision doesn't activate.
Lv.5 MetalGreymon EX10-008 R Ultimate | Virus | Cyborg <Reboot> [On Play] [When Digivolving] Give 1 of your opponent's Digimon <Collision> and "[Start of Your Main Phase] This Digimon attacks." until their turn ends. --- [Opponent's Turn] [Once Per Turn] When attack targets change, if this Digimon has [Greymon] in its name, trash your opponent's top security card.
Lv.5 MetalGreymon EX10-008 R Ultimate | Virus | Cyborg [Digivolve] Lv.4 w/[Greymon] in name: Cost 3 <Reboot> [On Play] [When Digivolving] Give 1 of your opponent's Digimon <Collision> and "[Start of Your Main Phase] This Digimon attacks." until their turn ends. --- [Opponent's Turn] [Once Per Turn] When attack targets change, if this Digimon has [Greymon] in its name, trash your opponent's top security card.
Lv.5 MetalGreymon EX10-008 R ultimate | Virus | Cyborg [Digivolve] Lv.4 w/[Greymon] in name: Cost 3 <Reboot> [On Play] [When Digivolving] Give 1 of your opponent's Digimon <Collision> and "[Start of Your Main Phase] This Digimon attacks." until their turn ends. --- [Opponent's Turn] [Once Per Turn] When attack targets change, if this Digimon has [Greymon] in its name, trash your opponent's top security card.
Lv.5 メタルグレイモン EX10-008 R 完全体 | ウィルス種 | サイボーグ型 ≪再起動≫ 【登場時】【進化時】相手のターン終了まで、相手のデジモン1体に≪衝突≫と「【自分のメインフェイズ開始時】このデジモンでアタックする。」の効果を与える。 --- 【相手のターン】[ターンに1回]アタックの対象が変更されたとき、このデジモンが名称に「グレイモン」を含むなら、相手のセキュリティを上から1枚破棄する。