Activated monster effects can be broken down into Quick, Trigger and Ignition.
A triggered effect will say 'When <something>, <do something>. You activate these whenever the condition is met, regardless of whose turn it is.
Quick Effects are Spell Speed 2 effects and can be used in either turn also. Many of them can only be used in the opponent's turn. You can recognise a Quick effect by various ways - if it specifically says it can be activated in the opponent's turn, then it must be Spell Speed 2. If it chains to other activations, such as effects that negate others, then it is a Quick Effect. If it is used in any other phase than the main phases, then likewise it must also be Quick and can therefore be used in either turn.
If the effect has nothing to identify it as either of the the above, then it is an Ignition Effect. These are spell speed 1, and can only be used in your own main phases.
No. One of the conditions placed upon Flip Summons is that the monster can not have declared an attack that turn - even if the attack was negated or otherwise halted. If a monster declares an attack and Book of Moon is used to turn it face-down, then as it declared an attack, you are unable to Flip Summon it that turn.
No, it is an Ignition Effect monster and can only be activated in its controller's main phases.
No. As soon as you enter the end phase, Fiendish will effect the monster.
The answer to this question can vary. Unless the card that Special Summoned the Gemini Monster specifically says otherwise, the Gemini Monster will be treated as a Normal Monster. If you have not already Normal Summoned this turn, you can perform said action on the Special Summoned Gemini Monster. There may be cards such as Black Brutdrago that states "The Special Summoned monster is treated as an Effect Monster, and gains its effect." In this case, as it states, the Special Summoned monster gains its effect while it is on the field and you do not have to resummon it.
It depends on what the effect is.If it is a Quick Effect, or a Triggered Effect, then it can be used once in either turn.If it is an Ignition Effect (which it will be if it doesn't specifically respond to something, or specifically say it can be used in the opponent's turn) then it actually means 'Once per your turn'. While confusing, it'd technically be redundant to say 'once per your turn' on an Ignition Effect, they can only be activated in your own turn anyway.
No. One of the conditions placed upon Flip Summons is that the monster can not have declared an attack that turn - even if the attack was negated or otherwise halted. If a monster declares an attack and Book of Moon is used to turn it face-down, then as it declared an attack, you are unable to Flip Summon it that turn.
The 'once more' bit is restricting you to using this effect once only in a turn. Even if she destroys another monster with her next attack, she cannot declare a third attack.
Yes, using a monster's effect in absolutely no way stops it from being tributed later on in the turn.
As Destiny Hero - Plasma's equip effect is a "Once Per Turn" effect, yes it can, and the existing monster is destroyed.
No, a monster cannot manually change battle position on the turn it was special summoned, though it can be changed by an effect.
Unless another effect puts it back to its original place.
No, it is an Ignition Effect monster and can only be activated in its controller's main phases.
Yes, you can attack with the Tribute Summoned monster unless a card effect tells it not to or it is after the Battle Phase.
yeah it can but its no use cause its destroyed during the end of the turn that you monster reborn it on the proper card effect.
The effect he uses to destroy a monster, is an Ignition Effect, so can only be used in your own turns, in your main phases. However his counter-adding effect will add counters in either turn.
You can manually change the battle position of a monster once per turn, (but not on the turn it was set or summoned from hand) If you flip a monster face down with Book of Moon or use the effect of Sonic Bird, then you are allowed to flip summon them in the same turn.
Substitoad is an Ignition Effect monster, so can only be used in your own main phases.