Gertrude the Wombat
VOR tracking is dead easy. Find an instructor who can explain it clearly and show you how to do it in flight, and if yours can't then get another one.
Most VFR (i.e. PPL) routes can be planned either mostly or partly on VOR radials and having the VOR receiver (the CDI) tuned to the nearest VOR and having the bar centred is a great assurance that you are on track, and the workload is extremely low.
At PPL level, forget the stuff about what happens when the CDI is set to say 270 instead of 90!!! Nobody would do that intentionally en-route. When you track a VOR you always have the same TRACK set on the CDI as the HEADING you are flying on the DI (plus or minus the wind offset of course). So if you set a TRACK on the CDI of say 090, the required HEADING to hold that track might be somewhere between 070 and 110 perhaps, but the point is that both of the figures will be roughly similar. (the CDI will work when set to the reciprocal but it works backwards...)
As you pass over a VOR, the TO flag changes to a FROM flag but you carry on flying as normal because nothing else has happened.
The only time you deliberately turn the CDI setting (the OBS) to force a FROM flag to appear, with the bar centred, is for position fixing. This you will have to do for the PPL, but it's dead simple.
A and C
Do you have a reference for "every IFR approved GPS is BRNAV approved"? This certainly wasn't the case last time I checked, some months ago. No handheld GPS is likely to "ever" be IFR approved, and very few school/club planes will have one that is, except possibly a GNS430 but that is such a complex product most owner pilots with one in their plane don't properly understand it! A BRNAV approved GPS is authorised for en-route nav at FL95 and above.