Hi Gianluca,
OS Property has feature to allow registered-users to save their search criteria at advanced search page. For example, in advanced search page, you search properties that have 2 or more bathroom. And click on search button, the result will be shown at the bottom. And then, you can click on Save search list button. The search criteria will be stored in your account. From menu layout "Registered: search list" you will see all your search list, click on it, you will go to the advanced search page with saved criteria you selected before. Of course, the new results will be shown at the bottom of page.
Regarding to second question, OS Property has the availability calendar, but for customers to make the booking request, not the meeting between agents and customers.
Thanks
Dam