You can do it by using two variables, for example vStart and vEnd, and an action that can be assigned to a variable change or to a button. User enters Start and End dates in the input boxes (or calendar objects if you prefer), and clicks the button. Action will be "Select in Field" Field: Date
1. Yes. There are multiple ways to create variables, but since you have to create input box, you can define them right there. There is button "new variable" in the properties. 2. In the button properties - see Actions tab.
See attached example. You have to enter both dates, and click the button after that.