A few releases ago Mathworks introduced a changes section at the bottom of the documentation page. Other than that, it is simply a case of comparing documentation pages.
There is no standard way. There is a reason I keep my ifversion function on the file exchange up to date. Instead of try catch blocks (which can get messy, especially with multiple options), I use ifversion to branch my code. That way any errors will keep making sense (your code can throw an error about the parameters if there is a file access error on releases where you need the version in the try section).
Edit so it doesn't get lost (thanks Steven, I will try to remember to suggest them in on the FEX description page):
If you don't want to include ifversion in your code, you can probably use either verLessThan (introduced in release R2007a) or isMATLABReleaseOlderThan (introduced in release R2020b).
