Why specifically "Orchestrate"? At a high level it's the underpinnings of the parallel engine, a product that was aquired from Torrent Systems in 2001. If you are new to DataStage, first order of business would be the guides that ship with the product, for example the Parallel Job Develope...
Nope, it's simply the fact that all colums in the stage must be bound into the query. Each must mention all four, so if you don't want to update all fields you'll need to pre-qualify your actions and use two separate links.
I'm trying to help you help us and all you've done is repeat yourself. Have you considered the fact that perhaps posting the actual error message you are receiving might help?
Still, doesn't matter. Having an "identity column" (or any other surrogate value) with a 3 in it doesn't make it "the third row". It's not sequential media, after all. That's not to say that based on very specific conditions and/or sort orders, you couldn't identify the third rec...
I for one have no clue. All the docs mention is actions being "logged" which I assume means the job's log. Why not ping your official support provider, let us know what you find out?