The mouse droid thing is unverifiable, and thus largely considered to be bullshit.

The Beru voice is either dubbed by a different actress, or a different take of the same actress was used, in the 1977 mono version. The 1977 stereo, 70mm six-track, 1985 remix, 1993 remix, 1997 SE mix, and 2004 SE remix all use the same take/voice, but the mono mix uses a different one.

None of the mixes use the actress' real voice.

And the mono mix was the last one made, and the one made with the most attention to detail and care, since it was the version that the majority of the country would see. But (like the Beatles' albums), since "mono" has since become a dirty word, the stereo versions have been used since, despite the fact that they weren't considered the "real" version at the time.

And Lucas has made changes prior to the SE - he added Episode IV: A New Hope and reformatted the crawl in 1981, and he (possibly) changed the brightness of the Artoo-in-the-canyon scene (to make it look slightly darker) in 1993 for the Definitive Collection laserdisc, though this is unconfirmed - it's possible that prior releases were incorrectly color timed, as we don't have a reference to compare them to.