Cards will always go to their owner's (the player who came to the duel with that card in their deck) hand, deck, graveyard, etc, regardless of who controlled the card at the time. Card ownership never changes during a duel, unlike card controllership.
Only very specific cards can put one of your cards in the opponent's hand - Exchange and Amazoness Chain Master are two.
Infestation Pandemic will make it so your Creature Swap can't do anything to their Iswarm monsters. That means they have a choice - pick an Iswarm monster, meaning Creature Swap's resolution will fail and nothing will be exchanged. Or if they have a non-Iswarm monster, they could pick that instead and let that be exhanged with your chosen monster.
Well, you can't really. it matters on your pokemons speed and evaiseness. it happens randomly
Assuming the defending monster is also in attack position, both monsters will be destroyed.
Summon Limit restricts the number of times you can Special Summon. Scapegoat summons all 4 tokens at once, so it's a one-time summoning, so your opponent can still summon one more time for that turn.
Two Watthopper will protect each other from being chosen as attack targets or targets of targetted effects controlled by the opponent.
ok if it says deal X damage to target opponent than deal X damage to opponent and NOT creature. if it says deal X damage to target creature than deal it to the creature and NOT the player. if it says creature and player deal it to a creature and a player ect. the point is you will get a strait awnser if you just READ THE CARD, AND NEVER BEND WHAT THE CARD IS SAYING. ex: if it says get a creature from the grave and you get a instant you are bending the rules (it happens ALOT).
Your opponent's Windstorm of Etaqua changes the battle positions of all face-up monsters you control, then your Creatue Swap swaps your monster and your opponent's monster, since Creature Swap's effect only says that those 2 monsters can't change their battle positions for the rest of the turn, so the position change before the swap is legit.
Since you don't attack creatures in Magic (you declare attacks, and the opponent may choose to block if he wants) then it's almost a moot point. Technically a Planeswalker could become tapped and be attacked, however the outcome is no different. Nor is there any difference if a creature declares a block, and then becomes tapped.
What happens is you choose a monster on your opponent controls. Then you choose monsters in your graveyard to remove from play. But you have to remove monsters from play equal to the Level of your opponent's monster. Then your opponent's monster that you chose is destroyed. Eg. If you wanted to destroy Giant Rat, then you would have to remove 4 monsters in your graveyard from play because Giant Rat is Level 4.
Infestation Pandemic will make it so your Creature Swap can't do anything to their Iswarm monsters. That means they have a choice - pick an Iswarm monster, meaning Creature Swap's resolution will fail and nothing will be exchanged. Or if they have a non-Iswarm monster, they could pick that instead and let that be exhanged with your chosen monster.
a moose attacks with it's antlers
Assuming that the effect of "The Fabled Unicore" is active (therefore, assuming that you and your opponent have the same number of cards in your hands), both the monster effect that was activated and Doomcaliber Knight will be destroyed.
Confusion Chaff will resolve as normal. Note that Earthbound Immortals say "The opponent cannot select this monster as an attack target" - this is not happening here. The opponent is not declaring any attacks against your Earthbound Immortal.
Run!
Predicament
it will be considered a foul then the ball goes to the opponent.
Nothing happens. You just have alot of creatures. You can use it in the creature arena.