In this tutorial about version control and Construct, there is a warning that versions are not backward compatible and collaborators should refrain from updating the C3 version (rXXX).
But I haven't found an easy way to stop the updates programmatically. How do I stop the updates for those using the online editor? It is unfortunately not sustainable or feasible to rely on everyone hit the correct button on the popup to decline instant updates.
I'll also add that this is for students that are using an Access Code.
Also note that when Construct updates, make sure everyone on your team updates at the same time. Construct project files are not backwards compatible - i.e. you can't open a project saved in r200 in r100. Similarly, while using source control, you cannot merge changes made in r200 back in to a project saved in r100 and keep using it in r100. Since the file format is not backwards compatible, you may corrupt the project. If everyone on the team updates at the same time, you'll avoid this problem.
https://www.construct.net/en/tutorials/collaborate-construct-2390/conclusion-6