If you ever were to reinstall an older version of GameMaker you may find that it informs you that a project contains newer functionality that old version cannot support, and so the project is going to be opened in read-only mode in order to stop any potential for breaking the project.
This dialog is giving you correct information and in most cases 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.
Changes Covered In This FAQ
2022.8 Tiles layer encoding format
2022.2 Test tracks in Sequences
2022.8 -> Older versions
The 2022.8.0 version introduced the new "run length encoded tiles" feature, which required the project version to raise so that older versions of GameMaker would not try to open the project and allow you to accidentally wipe your tile layer data from your rooms, as the old version of GameMaker is not able to show you that your rooms still contain the tiles you added in the newer IDE (and the old runtimes would not build the new tiles correctly if you were to try running the project).
If you have edited a tile layer inside the project after opening the project in 2022.8 or newer and you find that your room's .yyp file now uses the newer format, then please do not attempt to follow the below steps. Stick with the current IDE and runtime version.
If you have not edited the project much/at all in 2022.8 or newer and you have not attempted to do anything with tile layers in your rooms, then you can do the following:
1. Ensure GameMaker is closed/the project is not loaded, then find the project on your computer and first of all check that ALL of its rooms are still in the OLD format (for this sample project, I will need to check these two rooms)
2. Open each room's folder and then edit its .yyp file in a plain text editor of your choice.
3. Search for the text "TileCompressedData" (it's written in the text file with the quotes, so with/without will work).
If this text is FOUND, stop. This project should not be edited further and you should return to using the current GameMaker version.
If this text is NOT found, repeat steps 2 and 3 for all rooms in your project (just to be sure).
4. Assuming none of your rooms contained the text above, then open the projects' main .yyp file in a plain text editor of your choice:
3. Search for and then lower its resourceVersion value down to 1.5, 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.
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. Search for and then 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.