I think this qualifies as a stretch on your part. C3PO was in an entirely different state in EP2 (internally and externally). More importantly, in EP4 he is not only operating with a revised memory, but he does NOT reveal himself as "C3P0" to Uncle Owen. Owen has no particular reason to identify this particular protocol droid--especially after so many years.
In short, there is no contradiction or plot goof--unless you really work hard to make it so in your mind.
That said, I'm not yet certain if those scenes will even be used and/or needed in The Prologue. But please do alert me of any other inconsistencies that exist in--or between--the prequels, because this phase of production requires me to think at the 'story board' level. It is not until later that I will begin to micro-analyze the details in all of the footage that is needed to support the story.