Rulings
Q1: This card doesn't have a level. Can I still digivolve into it and into other cards?
No. Cards that don't have levels can't be digivolved from, and you can't digivolve into this card. (Other than through special digivolutions.)
Q2: This card’s effect reads “you may trash 7 or more digivolution cards from the bottom of 1 of your Mother D-Reapers,” but can I choose to trash 8 or more digivolution cards when playing this card.?
Yes, you can.
Q3: There are 8 digivolution cards under EX2-007 Mother D-Reaper, and BT9-109 X Antibody is the bottom card. Does the "you may trash 7 or more digivolution cards from the bottom of 1 of your Mother D-Reapers to set this Digimon's play cost to 0" effect activate when this card is played?
It can activate in such cases if you declare to trash 8 cards and then trash 7 cards except for X Antibody.
Q4: I am in a situation where I have 8 cards, including one BT9-109 X antibody, as the digivolution card for my EX2-007 Mother De Reaper. When I play this card, can I activate the first effect of this card?
Yes, it activates. If you can destroy at least 7 cards from the bottom of the digivolution cards, excluding cards that cannot be destroyed, the play cost you pay will be 0.
Data Sources
Lv.- Reaper EX2-055 R D-Reaper | Ability Synthesis Agent When you would play this Digimon, you may trash 7 or more digivolution cards from the bottom of 1 of your [Mother D-Reaper]s to set this Digimon's play cost to 0.<Rush> (This Digimon can attack the turn it comes into play.) [When Attacking] You may place 2 [ADR-02 Searcher]s from your trash under this Digimon in any order as its bottom digivolution cards to unsuspend this Digimon.
Lv.- Reaper EX2-055 R D-Reaper | Ability Synthesis Agent When you would play this Digimon, you may trash 7 or more digivolution cards from the bottom of 1 of your [Mother D-Reaper]s to reduce this Digimon's play cost to 0.<Rush> (This Digimon can attack the turn it comes into play.) [When Attacking] You may place 2 [ADR-02 Searcher]s from your trash under this Digimon in any order as its digivolution cards to unsuspend this Digimon.
- Reaper EX2-055 R D-Reaper | Ability Synthesis Agent When you would play this Digimon, you may trash 7 or more digivolution cards from the bottom of 1 of your [Mother D-Reaper]'s to set this Digimon's play cost to 0. <Rush> [When Attacking] You may place 2 [ADR-02 Searcher]s from your trash under this Digimon in any order as its bottom digivolution cards to unsuspend this Digimon.
Lv.- リーパー EX2-055 R デ• リーパー | 能力統合タイプ このデジモンが登場するとき、自分の「マザー デ• リーパー」1体の進化元を下から7枚以上破棄することで、支払う登場コストを0にする。≪速攻≫（このデジモンは登場したターンでもアタックできる）【アタック時】自分のトラッシュから「ADR-02=サーチャー」2枚をこのデジモンの進化元の下に好きな順番で置くことで、このデジモンをアクティブにする。