Adobe support only the latest two versions of the CC apps and with CC2023 being the latest you only will have CC2022 as the other option. If you absolutely need CC2021 then the only way you can get it is via contacting Adobe support. To contact support follow the instructions given below 1. Go to https://helpx.adobe.com/contact.html?rghtup=autoOpen 2. Wait a bit on the page that opens up, it should automatically open a chat popup. If that does not happen then look for a call out/chat icon at the bottom right, click over it and the chat popup should open 3. In order to talk to a human type "AGENT" in the chat box 4. If you are not able to get to the chat window, then disable your adblockers, firewall, enable cookies/scripts on your browser. If it still fails then change your browser/machine/network.
P.S. Be mindful of answering anyone who sends you a private message. See the following for more information about scammers https://tinyurl.com/y7cfrr7y -Manan