Should I account difference in octaves between different guitar strings, like between 5th (octave A2) string and 4th string (octave D3), when I'm looking for intervals (for example perfect 4th) ? I mean, technically from theory standpoint, because I understand that they sound a bit differently.
Also, for example If I play P4 of G which is G-C notes, and if I play notes in reverse order and C and G are in different octaves is that considered a different interval? I think not, but what confuses me is that being in different octaves the actual half-step distance between notes change (if G is in the next octave then the distance is 7 half-steps, or P5), while the definition of P4 says that half-step distance should be 5 half-steps.
So, the rule is that if notes of some interval are in the same octave then the order they are played doesn't matter, but if notes are in different octaves then the order may matter?