In May 2018 the DB11 AMR was introduced. It had received vast improvements over the outgoing model, such as a power increase to 639 PS (470 kW; 630 hp) from its 5.2-litre AE31 twin-turbocharged V12 engine, revised shift programming for the 8-speed automatic transmission for quicker gear changes, firmer and stiffer rear suspension, improvement in 0–97 km/h (0–60 mph) acceleration time to 3.5 seconds and an increased top speed of 335 km/h (208 mph). Other unique features include a more aggressive exhaust note in Sport & Sport+ mode, black roof, dark interior trim and new 3.5 kg lighter, 20-inch forged alloy wheels.
Does anyone know if any or all of these improvements (especially the improved firmer and stiffer rear suspension) continued to be used in subsequent DB11s built since the AMR model name was discontinued in July 2021?

 

All those features carried over to the non-AMR DB11 V12 except for the cosmetic items

 

What's the first model year to get those improvements?

 

The DB11 AMR was introduced for the 2019.5 model year and discontinued for the 2022 model year. That's when the standard DB11 V12 received all the chassis and performance enhancements as standard.