Unfortunately not. As is the case with nearly all frequent flyer programs, it is the airline who markets the flight and who’s code appears on the ticket and not the operating carrier that dictates your earn rate.
KLM have no earn arrangement with velocity, so although they’re operated by Etihad virgin Australia will treat it as a KLM flight and you won’t earn anything for these flights.
Etihad will not recognise your velocity platinum status because again they’re the operating carrier but they don’t own the ticket, but in regards to the lounge access I am 99% sure that yes you will get to use Etihad lounges. I don’t know off the top of my head, but I find it highly unlikely that KLM would have their own lounge in Abu Dhabi given they only have one flight a day, so they probably let their customers use partner Etihads lounges.
If you want to check to be sure regarding the lounge access policy, I’d suggest a call to Etihads customer service team as they’d be able to clarify their policy in no uncertain terms. Most airlines will allow access to passengers who hold status, but only when you hold a ticket for an onward flight ticketed by a partner airline (like virgin or air Berlin).