I Was Wondering If I Have A Horus Lv. 6 Or A Lv. 4 On The Field And I Creature Swap What Happens? Do I Get The Opponents Monster And They Don't? Because Lv. 6 Is "unnafected" By Magics And Lv. 4 Cant Switch Control. So What Happens?

There are only two possibilities in this situation:

1) Creature Swap fails and is sent to the graveyard because it doesn't have legal "targets".

2) Creature Swap cannot be played because it doesn't have legal "targets".

Creature Swap must trade the monsters or it cannot function and neither monster is switched. I don't remember which way it goes at the moment, though, but one of the two scenarios is correct.

I put "targets" in quotes just because Creature Swap doesn't target.

#2 is the correct one. Cards can not just "fail" and be sent to the graveyard. If you were to activate Creature Swap in this situation it would just go back to your hand.

This is the ruling that makes me wonder about that. Although Creature Swap doesn't target like the card mentioned it does allow a card to activate, but get negated.

Actually, card effects CAN "fail" in the case of Horus LV6.

However, for Horus LV4, if it's the only face-up monster on your field, you would not be able to activate Creature Swap in the first place since it clearly dictates that its control cannot change, so it's not a legal target.

Horus LV6 CAN be selected, but since it remains unaffected by Magic Cards, the effect would resolve without monster's being switched (you do not get a "Free" monster) since BOTH monster's have to switch places for it to successfully resolve.

is it possible to use creature swap when the controller has no monsters on their side of the field (if so this card is deadly if used properly)

Netrep says!....:

Therefore, no. I believe this question has been answered in the rules of dueling section, but you gotta search for it.