As of the 2022.2.1 release you may find that opening a project in a newer version of GameMaker and then rolling back will now inform you that the version of the project is too new and so the project is going to be opened in read-only mode in order to stop any potential for breaking the project.
In most cases, this is correct and you should just return to using the current GameMaker release, rather than following this guide any further. However, this guide will give you information on the possible/likely reasons you are seeing that read-only message and how you can potentially edit your project in such a way that you might be able to use the old GameMaker IDE again.
ALWAYS back up your project before attempting any of the following troubleshooting sections, as it can be very easy to make a small mistake and break the project yourself.
2022.2 -> Older versions
The 2022.2.0 version introduced the new "text tracks in Sequences" feature, which required the project version to raise so that older versions of GameMaker would not try to open the project and cause it to become corrupted due to the old IDE not knowing about the new asset type if you used Sequences and particularly had tried to do anything with the new text tracks feature.
If you have edited a Sequence inside the project after opening the project in 2022.2 or newer, then we would not suggest trying to make the hand edit below. Stick with the current IDE version.
If you have not edited the project much/at all in 2022.2 or newer and you have not attempted to do anything with text-in-Sequences, then you can do the following:
1. Ensure GameMaker is closed/the project is not loaded, then find the project on your computer:
2. Open the main .yyp file inside that folder (pointed to by the red arrow in the image above) in a plain text editor of your choice.
3. Lower its resourceVersion value down to 1.4, then close and save the file:
You should now be able to open this project in the older GameMaker versions again. However, if you still get any issues, please restore your backup and return to the current version once more to be safe.