For the red pants, a Hue/Saturation layer, choose Reds, and lower the Lightness slider all the way to -100.
For the rest, I don't have any tricks, sorry. Just painstaking cloning.
What colour would you like? It would need to be another light colour.
This would be ideal if we could pull it off, but we'd have to be EXTRAORDINARY lucky to find another photo at exactly the correct angle, lighting, depth of field, size, etc.
No, if you look at the image sizes again, you'll see they're exactly the same.
Exactly the same pixel dimensions, that is. And that's the only thing that matters.
So the answer is: either method is fine. They both give the right result.
By "stripping out the profile" they mean to uncheck the profile box in the Save As dialog when you're saving the file.
I don't know what to tell you, sorry. This is just down to luck, it seems.
The first one is completely irrelevant, because you must work in changing light.
The second one ... well, that functionality is in Photoshop already, so I'm not sure what the benefit would be.
The third on ... how many screens do you have?