By the Book

Yes!  When you close the batch the year to date calculated fields are updated.  You also have to have all your batches closed to do the year end close.

Closing a batch simply means that you can no longer add contributions or donations to that batch.  You can however have multiple batches for the same day.  So there is no risk that you won't be able to enter a contribution into the software.

Once a batch is closed you can still go in and edit the contributions.  So if you entered the wrong amount, wrong donor or wrong fund designation, you can still make those corrections to closed batches.