Taken from the Official English Rulebook: ...However, for Monsters that are Level 5 or higher, you must Tribute at least 1 monster you control before the Normal Summon. This is called a Tribute Summon. Monsters that are Level 5 or 6 require 1 Tribute and Monsters that are Level 7 or higher require 2 Tributes. Monsters that are Tributed are sent to the Graveyard and the "Tribute Monster" you are Summoning is played in face-up Attack position or face-down Defense position (a.k.a. a "Set").
Yes
Yes, if you tribute Set them from hand, or flip them face-down using the effect of another card.
Yes, it may target face-down monsters.
Unless stated otherwise, tributes must be from amongst monsters you control. So you tribute the opponent's monsters for Lava Golem because he says so, but you could not for The Regulation of Tribe.
Yes. Face-down monsters can be tributed for tribute summons, card effects, etc.
Yes, monsters may be 'tribute set'.
Yes, face down cards on the field count.
Taken from the Official English Rulebook: ...However, for Monsters that are Level 5 or higher, you must Tribute at least 1 monster you control before the Normal Summon. This is called a Tribute Summon. Monsters that are Level 5 or 6 require 1 Tribute and Monsters that are Level 7 or higher require 2 Tributes. Monsters that are Tributed are sent to the Graveyard and the "Tribute Monster" you are Summoning is played in face-up Attack position or face-down Defense position (a.k.a. a "Set").
Yes, the tributed monster does not have to be face-up at all, it can be tributed while face-down.
You would tribute two of your monsters, then Set the Lv7 monster face-down in defence position.
No, face-down monsters are valid tributes, you are not forced to flip them first. There might be one or two cards that do require the tributes to be face up, but these will specify in the effect text.
Yes
Face-down monsters are indeed monsters for the purposes of cards which count monsters on the field or affect all monsters.However, if a card effect specifies a monster with a specific type, attribute, ATK, etc., it will ignore face-down monsters because those values are unknown in game terms.Note: monsters used as Equip cards are not considered monsters.
Yes, if you tribute Set them from hand, or flip them face-down using the effect of another card.
Yes, you can. Unless the card lore specifically states "...tribute one face-up [monster name]..." you can automatically assume that you can tribute it face-down. However, you must reveal to your opponent that the face-down monster is in fact Levia-Dragon - Daedalus before tributing it.
depends on the sacred beast one is 3 continues face up spell cards another is 3 continues face up trap cards and the last one is 3 fiend type monsters and you need to sacrifice 3 monsters because there so powerful