In terms of allowing/disallowing creation of certain events to not start/end on certain times, there are validation functions which you can inject into the configuration which control this.
https://www.bryntum.com/docs/calendar/#Calendar/feature/CalendarDrag#config-validateCreateFn
And the two following functions for validating move and resize.
In terms of editing using the EventEdit feature, you can add validation to the fields in there by configuring them. You could add change listeners to the start and end date fields which mark the field invalid if you don't like the value.
https://www.bryntum.com/docs/calendar/#Scheduler/feature/base/EditBase#config-items
