I think any question they ask here will be a practical application of data streams.
Basically, not every printer uses the same control characters, so they 'should' give a list of functions, and then the question will say: 'Construct data stream to do this' or 'What does this data stream do'.
However:
Page throw:
I think the interpretation here is simply for a 'new page' code. Some old printers used to do this with Chr$(12)
Then you have Chr$(13) which is your CrLf (Carraige Return - back to left side of page, Line Feed - New Line)
This can be done separate with Chr$(10) [Linefeed only] and Chr$(26) [CR only]
Note that Chr$(10) + Chr$(26) is the same thing as Chr$(13)
I've seen a newer-older printer code whihc is simply PA(x) where x is a number.
Font change:
Your old (mega old) printer would have had a number of built in fonts, which you had to use codes to change to. Dont ask me what any where, because I have no idea. Again it depends on the printer.
I think they just mean font change, because formatting doesnt 'really' come in here...
Line Spacing:
I've seen an old code simply LnS(x) which does this... (Where x is a number)
I'm sure you could make up codes if you had to, say they were from your old XNT-10 printer (also make up printer name & model) and then no marker will have any idea.