So “Aid” and an effect that granted “Temporary HP” would stack since…

A monk using a quaterstaff, does versatile die go up to a d10?

A monk using a quaterstaff. When their martial arts die increases to d8, does versatile die go up to a d10? and later lvl?

How would the Goblin’s Fury of the Small feature work with magic missile?

Does something that is classed as a ‘reaction’ always occur before the trigger?

A save is DC15 and has extra effects if failed by 5 or more, does that mean at 9 or at 10?

If Calm Emotions supress a frightening effect…