Trying to use V21 for the first time and I keep running into bugs that were not present in V20. How can I make the files I have changed in V21 readable in V20? Frankly, every time I update to the latest version I have difficulties and feel like I am doing Number One's debugging for them and paying for the privilege to boot. So why do I keep upgrading? Hoping that a long standing bug (random crashes when using outputs such as plotting and reports) will be fixed at last. Reminds me of the definition of insanity - repeating the same thing over and over but expecting a different outcome. :(
You can go back to V20 but you would need V20 (or less ) files. This is not unusual for files generated in a specific version cannot be used in previous versions. I however have found V21 to be pretty stable with no real catastrophic issues and been running it since it launched last July.
If you find a bug it better to report it rather than using the forum.