NebKher

Can the new version of NebKher's gold be applied to items?

Nothing in the card text says that you should use opponent's items, so you are using your own.

If I copy Taka's gold with NebKher, how does swapping golds work?

As usual - verbatim.

NebKher's alt blue: "Split the board into two sides with a straight line of spaces drawn through you space. **This turn:** Units on either side of the line cannot interact with objects and spaces on the other side of the line, as if they did not exist." what's meant by objects? Does it include tokens, heroes and minions?

just remember that each instance of movement is a single step.

Using NebKher's gold to copy Death Grenade: 1. Does it create an illusion token? 2. Does it trigger the end of round effect, because "that token" references the illusion in this case? 3. Will the illusion token even stay on the board, given that in the clearing step it's targeting the grenade token?

1. Yes. 2. No, because it's not a grenade. You didn't place the token which the card text is refering to. There was a replacement effect. 3. Yes.

When NebKher copies Bain, can he give someone the bounty marker, even if the marker was used before?

Nope. Line 5: "do not use markers"

Can NebKher's gold place Trinket's turret (for example, if NebKher uses his gold on Trinket's gold), since the turret is not a token?

Follow the text exactly as written. ||Yes. Not just place, but also explode an already placed one with green, for example||