I don't have alarm on but an alarm icon were appear on top right corner
Yup, I face the same issue as well even though I do not use the default clock app. Not a solution, but, restarting the phone helps.
it helps but icon will come back again and again..
The Android 10 update is so close now that it's better to wait and see if it will fix this issue. It's unnecessary to go through all the steps needed to find a bug which might not exist in Android 10
Have you tried removing all your alarms and created them again?
Could also be that there's some 3rd party app that has set a reminder. It's a bit unfortunate that that the system can't tell you where the alarm/reminder comes from. There are tons of threads discussing your issue in a lot of manufacturer forums. For one guy it was tasker, for another it was pandora and so on. So please go through all your apps that could maybe have an alarm function. Probably not games but most other apps.