I think 2013 the last year for reasonable emissions equipment, so that 2011 should be fine emissions wise.
It kinda depends on how they are meeting the requirements ...
For example my 2005 Kubota
L5030 gross 52 HP meets the standard without any computer aided sensors ... Which is considered tier 2.
In 2008 is when tier 4 starts (no tier 3 in this engine size) they cut the required Particulate Matter by half, but everything else is the same as tier 2 ...
Also kinda interesting is that my 2021 25 HP SCUT has similar numbers required as my 2005 Kubota does, while my SCUT is commonly referred to as "no emissions" that's not entirely true, as you can see that there is indeed a requirement, which I believe is met by tightening up clearances in the cylinders, but also improving injector pressure and spray patterns, but it has no computer or other sensors ...
Comparing the requirements of my 2021 SCUT to the 2011 Deere 35D are also very similar, with only slightly lower numbers in two areas ... So maybe it doesn't have a computer and sensors ... If it does, it would easily turn into a nightmare, being built in the "teething" time period of these new standards ...
Probably easiest way to tell, is turn on the key, if it has a "check engine" light, it does! I'm not seeing anything that looks like a chk engine or wrench in here ... Although I'm not sure what they all are?
I'm thinking that the less than 8kw tier 1 engines are about as close to old school engines, look at there allowed numbers!