My company has no specific instruction on that procedure.
As a general rule, it's better to have your actual landing rwy in your primary.
Having said that, side-step are usually 'offered' by TWR late on final.
Airmanship would suggest to keep both heads up and fly it visually as prescribed.
If you're just to side-step on a parallel rwy (within 30 deg), you're still covered with you GS mini function.
If you feel/need to change your rwy at this stage, 1000' could be a sensible limit for any mcdu input (as in LVP ops philosophy).
In theory, if you have to go-around without specific instruction, you must follow your instrument missed approach proc.
In real life, competent ATCO will clear any doubt beforehand by giving you on final specific instruction should you need to G/A.
For your other questions:
1) Yes, company proc...even for rwy backtrack...
2) "Continue" call is just a confirmation that we're not going around
, 500' AAL...but again company proc.