You may flip Ultimate Offering face-up during any phase of play and during either player’s turn. This much is fine. You can only activate its effect of additional normal summons during YOUR Main Phase 1 and 2, and during your OPPONENT’S Battle Phase. This means you could flip it face-up during your opponent’s Main Phase 1 and then activate its effect during their Battle Phase.
The Summon produced through the effect of “Ultimate Offering” may be negated only if that Summon was the first link of a Chain.
A player may not Tribute a monster to be Summoned by “Ultimate Offering” until that monster is Normal Summoned/Set to the field.
Netrep Q&As:
Q: If I declare an attack and my opponent uses the effect of “Ultimate Offering” to tribute the monster I am attacking for a higher level monster, does my attack continue?
A: A replay would occur because the target of your attack is no longer on the field. Play will return to the Battle Step. You are not forced to attack the new monster. Curtis Schultz, 12/08/2003
Q: If a player has an active “Ultimate Offering” on the field, can their opponent use the effect?
A: Only the controller of “Ultimate Offering” can use its effect. Curtis Schultz, 02/13/2004
Q: Can “Ultimate Offering” chain to itself?
A: Yes, it can. bishop 02/23/2004
Q: Can you use the Spell or Trap cards brought to the field through the effect of “Magical Hats” as a Tribute using Ultimate Offering?
A: Yes, you can offer the face-down non-monster cards selected from the effect of “Magicial Hats” as Tributes for a Tribute Summon using “Ultimate Offering.” The non-monster cards are being treated as monsters during that Battle Phase, so it will okay to do this. You would need to resolve “Magical Hats” first in order to get the non-monster cards into play, then activate the effect of “Ultimate Offering” afterwards. Curtis Schultz, 02/02/2004
Q: If an Effect Monster such as “Sonic Bird” is summoned by the effect of “Ultimate Offering” during the opponent’s Battle Phase, will the effect of the monster still activate?
A: The Summon performed by “Ultimate Offering” during the opponent’s Battle Phase is still considered a Normal Summon… So if you choose to use its effect and Summon a “Sonic Bird,” the “Sonic Bird’s” effect will after it is successfully Summoned. Obviously this will not happen if you were to Set the “Sonic Bird.” Curtis Schultz, 01/25/2004