2020-04-17 : If the target creature is an illegal target when Surly Badgersaur’s last ability tries to resolve, the ability doesn’t resolve. If it’s a legal target but Surly Badgersaur is no longer on the battlefield when the ability resolves, the target creature won’t deal or be dealt damage.

2020-04-17 : If you discard a card as a cost to cast a spell or activate an ability, Surly Badgersaur’s triggered ability resolves before that spell or ability but after you’ve chosen targets for it. If you discard a card while a spell or ability is resolving, that spell or ability finishes resolving before Surly Badgersaur’s triggered ability does.

2020-04-17 : Surly Badgersaur’s abilities are triggered abilities, not activated abilities. They don’t allow you to discard a card whenever you want; rather, you need some other way of discarding a card, such as a cycling ability.