24 Sept 2021
The triggered ability will resolve before Old Stickfingers does. If Old Stickfingers is countered in response to its own triggered ability, you will still follow all the instructions of the triggered ability, using the chosen value of X.
24 Sept 2021
The ability that defines the power and toughness of Old Stickfingers functions in all zones, not only while Old Stickfingers is on the battlefield. While Old Stickfingers is in a graveyard, the ability will count Old Stickfingers itself, presumably using a single, withered stickfinger.