Based on this response, a question has arisen within me. Is there any service available to view the different options and rules proposed by airlines for a particular air route from AAA to BBB?
There are no freely available tools (that I'm aware of!) that will show you all available fares/rules for specific routes. Tools like the ITA Software "Matrix" tool will allow you to view the rules for a specific route/fare that it has returned in the search results - but even then it's not possible to view all fares. Several other airfare booking tools also display fares rules, including sometimes the airlines website themselves - but again these will only show rules for the fares returned in their search results.
There are a few paid tools that will allow you to query all public 'fares' on a given route, and view the corresponding fare rules. The most common two of these are Expert Flyer and KVS Tool. Both of these charge a monthly fee for access, and the exact level of detail available depends on which of their service levels you pay for.
Travel agents also also generally able to view all fares using their booking systems (aka GDS), however such systems are not available to the public.