I cannot tell which exactly manual is not working, since you did not mention that, but the online manual is available here:
https://adventuregamestudio.github.io/ags-manual/
The history of major changes may be found in "Upgrading from a previous version" section:
https://adventuregamestudio.github.io/ags-manual/UpgradingFromPreviousVersion.html
https://adventuregamestudio.github.io/ags-manual/
The history of major changes may be found in "Upgrading from a previous version" section:
https://adventuregamestudio.github.io/ags-manual/UpgradingFromPreviousVersion.html