Room Booking Calendar - A way to block just one room?

Is there a way I could just block a single room for a specific day and timeframe in that day?

Could I also Unblock a room that I have blocked for a day and timeframe in that day?

please clarify what you are doing.
Do you need to specify some time frames as not available for bookings?
There may be couple approaches. The easiest one would be to simply create an event with some custom type which will indicate the it is means blocked time.
Alternatively, you can have two kind of calendars in your app - event calendar and availability calendar.
You can mark available-not available times in availability calendar, then event calendar will load those as blocked time spans, very similar to what is done in this demo: … spans.aspx (you may need to restore and update NuGet packages in order to run the demo)