first synchronisation with google calendar

Hi,

Is it necessary to sync Easy Appointments with an empty google calendar for first sync or can it be done with a calendar with tasks already in?
I suppose all appointment tests should be deleted in EA before first sync to avoid conflicts.
I recommended it to my client but i need to know if tasks already in Google Calendar are not deleted after the first sync with EA.

Also, i read “Custom time interval for sync on each 5, 15 or 30 minutes” in features. Are there case sync interval are delayed?
I also need to be sure than my client can make an appointment manually directly in its google calendar with its time blocked in EA.

Thanks.