"CR" means classic rewards - basically it's Qantas' fancy word for an award seat.
The best way to search for these are via the multi-city tool (even if you're only looking for 1 leg) -
Make sure you select "Use points - Classic Flight Rewards only" and then tick the "Flexible with dates for all flights" when you select your dates.
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This will then come up with a full calendar view of award seats that are available.
You will then want to specifically look for any golden coloured ribbon - these denote business reward seat availability.
You do have to note sometimes though as some of these "business availabilities" are only valid on for example, 1 of 2 of the legs on that option - it'll be denoted with a little "i" symbol.
Looking for example - Singapore to London in April -
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There appears to be some business availability on some dates - click on the date and then continue - you'll then see what options there are.
01/04 actually looks decent - there's actually a direct business seat on British Airways (quite rare).
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You do have to be quick though as it's first come first served - what might be showing now might be snapped up in the next hour or even sooner.
This is the best way to secure outright business seats, as opposed to buying an economy ticket and then hoping for an upgrade using points at a later stage, which depending on the route, will be very difficult if not impossible for a Bronze member.
Good luck.