Compute damage based on the monster’s Level while it was on the field, not its level in the Graveyard or removed zone [sic]. This means you can Tribute “Embodiment of Apophis” or “Zoma the Spirit” to do 800 damage.[1]
If you Tribute a face-down monster, compute damage based on the monster’s original Level printed on the card.[1]
If you Tribute a face-up monster, the damage inflicted by "Dark Strike Fighter" is based on the Tributed monster's Level while it is face-up on the field.[3][4] If you Tribute a face-down monster, the damage inflicted is based on the monster's original Level.[4]
The "Jurrac Tokens" Special Summoned by "Jurrac Stauriko" only cannot be Tributed for the Tribute Summon of a non-"Jurrac" monster; they may be Tributed for purposes other than Tribute Summoning. Thus, you can Tribute them to activate the effects of "Cannon Soldier" or "Dark Strike Fighter".[5]