Automatic Calculations

By default an Excel sheet calculates the formula result automatically. This is indeed a great feature with the user only need to worry about the values in the cell, and any change in these values result in changes in the formula result  by its own.

How to remove Data Validations

There are multiple ways to do it and probably the simplest is to copy and paste an empty cell over the cell which contains the data validation. However if you just want to clear the data validation leaving the data & the format intact. Use the Clear All button on the Data Validation dialog box.