Key change

Wow, thanks Luke…
I’m aware some songs have a ‘key change’ during the song. Or it may be ‘goes up an octave, not sure which .
For anexample the song " please release me " (Engleburt Humperdink version ) is played on a diatonic harp, (1st line, -4 -4’ 4 -3 -4 4 2 )
Once the verse is played, it repeats.
Here’s my problem… When i listen to the song i notice that about the third time we play the verse, it seems to have gone into a higher key or octave.
Now i think if I were on a piano i could sus out where next to go.
But being on a pentatonic harmonica i can’t.
Question 1 how will iknow if it’s a key change or an octave ?
Question 2 If i’m needing to go up an octave how do i do it?
Question 3 if it’s a key change, do i just change harps for that particular piece (then back later ) and if so how would i know which key to change to? is there a ‘rule’?
A hard subject to explain, and perhaps difficult to answer.
But really appreciate your help, and glad that this site is here too cheers Luke Lol