what version of quick time should i use.
The version of QuickTime 10.x is linked to your version macOS, and you can’t upgrade or downgrade that separately from the other.
quick time not responding
It could be that the application is in some sort of loop, and not taking any input. This issue is not about the version. QuickTime Player would normally tell you if it can’t open of play a file.
- Try force-quitting the QuickTime Player application.
- Try restarting your iMac.
did allow me to choose quicktime 7
QuickTime 7 can be handy for (old) codecs that QuickTime 10 doesn’t support. They work independently, and won’t interfere with each other. Any application can theoretically give “not responding” messages.
but dont know how to set that as default
To set an application as the default for any given filename suffix (e.g. “.mov”), open the Get Info window for any such file. Then change ‘Open with’ (for this particular file), followed by ‘Change All’ (to apply the change to all files with that same suffix).
Choose an app to open a file on Mac - Apple Support