where can I download vaadin version 23 flow-crm-tutorial? coz when vaadin24 was released there is no option to download 23?

you can just switch to the V23 branch in github:

Thank you sir. Is there also anyway to downgrade version 24 to 23 and java 17 to 11? @useful-whale

Downgrade shouldn’t be too hard if you go to latest SB 2.7 & Vaadin 23.3, but lot of find and replace etc, due to javax->jakarta ee change. But, the true question is why can’t you pick Java 17? I assume that is the reason for V23. Java 20 was just out and less than 6 months to next Java LTS (21).