Rulings
Q1: "Neither party can minus the play cost they pay each other." What is the effect of
The effect is that when you pay a play cost, you can no longer minus that cost. This effect affects both players.
Q2: "Mutually cannot minus the play COST to be paid." Can I make it play with the "make it play without paying the cost" effect while the effect is activateD?
Yes, it can be made to play. The effect of letting it play without paying the cost is not an effect that negates the play COST.
Q3: "Neither can minus the play cost that each other pays." Can the effect of Digimon in Breeding Area minus play cost while the effect is activateD?
No, the play cost cannot be minus. No, the play cost cannot be minus each other's pay." The target player cannot minus the play cost, because the effect does not affect the card that activates the effect to minus the play cost, but affects each other's players.
Q4: Can't minus the play COST each other pays." Can I digicross while the effect is activateD?
Yes, you can digicross. However, the play cost cannot be minus by digicrossing. If you are unable to pay the cost, you cannot declare the card to be played.
Data Sources
Lv.3 Otamamon EX7-015 U Rookie | Virus | Amphibian/NSp [Digivolve] Lv.2 w/[NSp] trait: Cost 0 [All Turns] Players can't reduce play costs.
Lv.3 Otamamon EX7-015 U Rookie | Virus | Amphibian/NSp [Digivolve] Lv.2 w/[NSp] trait: Cost 0 [All Turns] Players can't reduce play costs.
Lv.3 Otamamon EX7-015 U Rookie | Virus | Amphibian/NSp [Digivolve] Lv.2 w/[NSp] trait: Cost 0 [All Turns] Players can't reduce play costs.
Lv.3 オタマモン EX7-015 U 成長期 | ウィルス種 | 両生類型/NSp 特徴に「NSp」を持つLv.2:コスト0 【お互いのターン】お互いは支払う登場コストをマイナスできない。