Do you know whether students have the ability to lift a hold or request after actually requesting the item?

Yes they can! If they go to the Library home page they will see an option for "My Account" located on the left and they need to click it. On the next page they will see "My Account (Five College Libraries Borrowing)" they need to click on the "Login" next to that. From there they will be able to see their requests and will be able to cancel them from there.