You can play either single-player, known in game as Solo Mode , where you proceed through a story of the cards involved playing against a computer opponent
If your opponent activates a monster effect in their hand, GY, or banishment (except during the Damage Step): You can Special Summon this card from your GY (if it was there when they activated) or hand (even if not), but destroy it during the End Phase
Yugo then found a crystalized shard of Yuya's memories, shattering it while he and Yuri both agreed that it was for the best Yuya does not remember them as they were
Generally, you may access the monsters in your Extra Deck at any point during your Main Phase and may Summon using the appropriate Summoning method, assuming you can do so
The equipped monster's effect, "Trap Cards, and their effects on the field, cannot be activated