Reverse gear practically gone ?

[Adrian @ SAS]

1st thing to check is the hydraulic circuit. Chances are you have a leaking master or slave & or air in the system.
Failing that & the push is correct, a similar result can come from a loose or incorrectly fitted clutch cover/diapragm.
In this case the box needs to come out.
On inspection if the clutch is ok, your next inspection is inside the box.
That being the three M6 x 1.0mm bolts (10mm head) retaining the interlock lower plate are likely loose together with the 2 M6 bolts retaining the reverse selector.
Follow oem manual for box disassembly, re-assembly procedure

[chez00]

^^^this. Also I find that often the interlock measures under spec (the "ball" on the interlock bracket). Reverse needs the biggest thrust/throw from the interlock to engage the gear so losing reverse is usually the first sign that the interlock ball is worn beyond spec.

[Extremer!]

As you have written it has always been difficult to engage reverse and on high RPM 4th crunches . Crunching 4th or any gear in high RPM in the Honda gearbox world is synchros . But in regards of the difficulty of engaging reverse that might be the shift change assembly . as they bend , or on the reverse change holder there is a ball bearing which might not be in it place any more .

Can you bring the car to Blacktown , to my store so I can have a look and take it from there ?!