Official Rulings
Can I play Explo-rover (WC 297) as an upgrade if my opponent sacrificed Lifeward (COTA 077) on a previous turn?
If I have Matter Maker (MM 349) in play, can I play Explo-rover (WC 297) as an upgrade when Star Alliance is not my active house?
If my opponent has Kaupe (DT 341) in play, and I've already played a creature, can I still play Explo-rover (WC 297) as an upgrade?
Yes to all three. Explo-rover’s ability allows it to be played as an upgrade anytime an upgrade could be played.
Source: Rulebook
Can I play Explo-rover (WC 297) as an upgrade if my opponent sacrificed Lifeward (COTA 077) on a previous turn?
If I have Matter Maker (MM 349) in play, can I play Explo-rover (WC 297) as an upgrade when Star Alliance is not my active house?
If my opponent has Kaupe (DT 341) in play, and I've already played a creature, can I still play Explo-rover (WC 297) as an upgrade?
Yes to all three. Explo-rover’s ability allows it to be played as an upgrade anytime an upgrade could be played.
Source: Rulebook
Commentary
Cards put into play by another card's effect (rather than being played from an out-of-play area such as the hand or discard pile) are not considered "played" cards. If an ability “puts” a card “into play,” bonus icons and “Play:” abilities on the card put into play do not resolve.
Source: Play: (ability)
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