2 Chain of Vapor Questions

[Smmenen]

1) If I cast Chain of Vapor on a permanent I control, such as a Mox, and then sacrifice a land to copy it, can I eat the second copy with Nivamgus Elemental?

2) If I cast Chain of Vapor on a permanent an opponent controls, and they sacrifice a land to copy it to target another permanent they control (say, a Mox), can I activate Spellskite to have their Chain target my Spellskite instead, and then copy it once more?   

[bactgudz]

yes to both.  The the player who puts the copy on the stack is that copy's controller, and the copy is instant spell while on the stack, so it's controller could exile it to Nivmagus (it doesn't matter who cast the original chain)...just be careful to communicate your retention of priority when you copy chain so you can exile the copy.
As to the spellskite, when his ability resolves, he becomes the target of chain and you are "that permanent's (the target's) controller" when chain resolves, so you can choose to copy.

[Smmenen]

What, exactly, is the proper procedure for one of those sequence?  Does Chain of Vapor -- the card -- go in the graveyard before, after, or simultaneous to announcing a second copy (either yours or your opponents)?

[Clariax]

What, exactly, is the proper procedure for one of those sequence?  Does Chain of Vapor -- the card -- go in the graveyard before, after, or simultaneous to announcing a second copy (either yours or your opponents)?

You carry out the instructions in order.  And then the last step is chain of vapor going to the graveyard.  So the new copy will already be on the stack before the original hits the graveyard.  (It won't resolve right then, just get put on the stack.)