Milan,
I don't have a concrete answer on whether it will only look for appointments during the delta period. Our initial thoughts were yes, but it looks like some additional research may be required. I do know that the only appointments/meetings that will be updated will be those during the delta period. If I find any other information out about whether it only searches for meetings during the delta period, I will post another comment response for you.
The answer to your other question about meeting requests is yes. When the meetings are updated on the organizers calendar, an update will be sent out to all attendees that they will have to accept before it is updated on their calendar.