Is it wrong to have two voices move from a perfect fifth to a perfect octave?

In short, these are perfect fifths or octaves that are approached by similar motion between two voices. But there are wildly varying rules for situations in which these fifths/octaves are okay: If neither the soprano nor the bass are involved, it's fine. If one of the voices moves by semitone, it's fine.

1. Can a fifth move to an octave?
2. What is wrong with parallel fifths?
3. Are unequal fifths allowed?
4. What are contrary octaves?

Can a fifth move to an octave?

188-189) As in two-part counterpoint it is illegal to approach a fifth or an octave in similar motion. You will be happy to know that this rule is considerably weakened in a 4-voice texture. It only applies between the outer voices, soprano and bass.

What is wrong with parallel fifths?

So what's wrong with parallel fifths? The issue is that the notes of a perfect fifth blend so well together that they almost sound like one note rather than two. This makes parallel fifths out of style IF that style demands independence of voices. Don't worry if this is not entirely clear yet.

Are unequal fifths allowed?

The reverse, a rising P5→d5, is acceptable voice leading (no deduction). Unequal fifths in either order, when descending, are acceptable (no deduction).

What are contrary octaves?

To my understanding a direct octave is when there is an octave followed by another octave going in the same direction (descending or ascending). A contrary one is when their is an octave after another one but they are going in opposite directions.