Tribute is only needed for the monster's Normal Summon or Set (or Special Summon in special cases). Flip Summoning does not require any tribute at all, regardless of what monster it is.
Torrential Tribute and Bottomless Trap Hole can only be used in response to a monster's summon. Attacking a monster does not summon it (note that if the monster is face down, this is a Flip and not a Flip Summon).
Generally, no. Synchro Monsters are initially Special Summoned FACE-UP. Therefore, there is not a need for it to be Flip Summoned. However, that Synchro Monster may be affected by a card effect such as Book of Moon. In this case, the Synchro Monster is changed to face-down Defense Position. You can then Flip Summon it when possible.
You put a monster in face down defense position BUT your not allowed to normel summon a monster in defense postion.
You cannot tribute summon a monster in face up defense position. You can either tribute summon a monster in face down defense or face up attack position. If you want to summon in face up defense, you need to special summon.
Setting is similar, yet not identical to normal summoning. a normal summon is when you Summon a monster onto the field in face-up attack position, whereas a set is when you normal summon a monster in face-down defense position. When a monster is set, it is not yet considered a summoned monster.
no the water monster must be face-up
No, a Tribute Summon follows the same position rules as a Normal Summon, so a monster you Tribute Summon is either face-up attack or Tribute Set into face-down defense.
Yes, technically that's a Set though, not a Summon.
No, it can't be special summoned except by Fusion Summon, even if you summon it and it is destroyed, it can't be resummoned from the graveyard. However cards like Blue-Eyes Ultimate Dragon can be summoned with Monster Reborn, if you properly summon it first, and then it goes to the graveayrd.
Yes, this is legal. You may perform one Normal Summon or set per turn, and as many Flip Summons as you wish.However you cannot Flip Summon a monster Set that turn, nor if you Flip Summon a monster, turn it face-down in the same turn using an effect, can you Flip Summon it again that turn. Lastly if a monster declares an attack, and is flipped face-down in response, it cannot be Flip Summoned that turn.
You can set the monster you tributed for, but the tributed monster is sent to the graveyard
Yes, monsters may be 'tribute set'.