Send them an email with a copy of the competing offer and politely ask if they can match. If there is a particular dimension that you care about, you...
Those questions are fine, although it might be better to ask them at a (virtual) visit day. You also want to talk to current graduate students to see...
Questions sometimes arise about the deadline for replying to offers. There is a pretty firm April 15 deadline for most American schools. You can read...