For future reference, I'll give a less-aging answer (it might even start out as outdated before it becomes indated in the future):
For previewing and testing an upcoming Godot version, and to make minimal techdemos of upcoming features (Without any fancy stuff that an actual game would have, like a title screen or even remotely complex gameplay, or high amounts of polish), it is fine to use an unstable Godot version if you're really careful.
But for making actual games, Don't use any Godot version whose version number doesn't end with .stable.
Examples:
- It is a good idea to use a Godot version like 3.3.stable or 4.0.stable because they stable
(note how the version number ends with .stable)
- It is generally Not a good idea to use a Godot version like 3.4 or 4.0 because these are not stable
(note how the version number does Not end with .stable)
