So there is no reason commercial pilots couldn't spend a couple hours practicing stall recovery and engine outs in a Cessna.

The way a pilot's rating works is you get your private pilot license which is the same as a driver's license for most 'general aviation' planes. In those, you are required to demonstrate stall and engine out recovery as part of the test. Theoretically, you can get your PPL with around 20 dual instruction, 20 solo. I solo'ed around 8 hours, and spent another 30'ish learning how to navigate and fly when things went sideways. For me, hour 7 was stalls and spin recovery. (fun, but glad I skipped lunch)

The Instrument rating allows you to fly IFR (in clouds and higher controlled altitudes. One of the tougher ratings of the series.

Commercial allows you to start flying stuff for hire. This usually starts with dropping parachutes or pulling banners. Theoretically flying someone from A to B and getting paid for it. Ironically, some gigs don't need Instrument to fly commercial. Brother-in-law does helicopter crop dusting and fire fighting on just a commercial ticket. You need 250 hours to qualify to take the test.

ATP is where you fly the big stuff. I forget the passenger/size limits - want to say it is near 20 seats. This is the rating where they ask for 1500 hours minimum before they allow you to take the test. For most pilots, this is where you start in the regional airlines and start working your way up to the majors (like Delta).

Unless you add a rating, every couple years you are required to demonstrate you still know what you are doing. Every time I've worked with an unknown instructor they make you go through the same stall/failure drills.

I believe (but I might be wrong) simulators might be cheaper than Cessna flight hours, plus you need training on the aircraft you operate since anything more elaborate than a 2 piston engine aircraft has a type rating and requires specific training.