1) How do you customize the drop down menu so that a user can only input a selected item and not anything unique? So if a user has "option1", "option2", and "option3" in the drop menu, tha'ts the only three things they can put into the input textfield

2) I am still working on optimizing my search, but it's a little slower than a user's typing speed.  I've noticed that when a user types fast and selects a drop down menu, the drop down will continue to open and close as the requests come back to the control, even after the item was already selected.  I don't know what the solution to this is, but I've considered disabling the autocomplete control after an option is selected.  The caveat is now if the user wants to delete the input and re-type something in, it'll be disabled.  Does anybody have a solution to this issue?