Some sites show it on the booking page, and if not, there are various sites* on which you can look up the flight number to see what aircraft type has been used historically. Sometimes several different types are cycled on a given flight (e.g. Boeing 777 and Airbus A350), but for many flight numbers it's always the same aircraft type.

For example, American Airlines has tons of both 737 and A320 aircraft, but AA858 seemingly always uses a 737-800 (B738):

https://www.flightradar24.com/data/flights/aa858

* e.g. flightaware.com and flightradar24.com

Depends on the route and on the airlines available. For example, Delta doesn't currently have the 737 Max, and I highly doubt they will order it in the near future. In Germany, Lufthansa doesn't have any 737 in its fleet anymore.

Not easily or cost-effectively. You can...

... book on an airline that flies Airbus only. There may be a few of those, but it severely limits choice in airline.

... try to determine which Boeing model is used, and be willing to walk away at the gate if the plane is changed out (losing the ticket, or at best incurring a typically large change fee).

Catchy rhyme. I could see it spread in the wider population in this form - it's memegenic :).

Until heads roll--actual criminal liability--then I'm afraid your point stands:

Catastrophic failures are a cost of doing business.