I'm also a BK user.
As for your questions:
1 - yes, it's a long standing program in the field, with regular updates.
2 - Define better. If you have some specific requirements, you'd have to state them.
3 - Yes and no. Any reasonably modern genealogy program can export and import GEDCOMs, so in that sense, yes. Can she shift from BK to say Family Tree Maker with absolutely no loss of data, probably not. Note, that the same is true for almost all programs. Very few programs can fully read the data sets from another program. So, if she wanted to shift from Family Tree Maker to Roots Magic, she'd likely lose data.
4 - What is special, from a computer programming issue, about Australia?
As for notes, you have to select to back up notes, images, media files, etc when you do the backup routine.