If using the graph editor, I would use the ANY state and add transitions between that to every state with a trigger param for each transition.
Then I would set the trigger with single frame enabled (see [SOLVED] Anim: triggering initial state leads to unexpected behaviour - #14 by yaustar) and also set the activeTime of the layer to 0 to ‘reset’ it. https://developer.playcanvas.com/en/api/pc.AnimComponentLayer.html#activeStateCurrentTime
No, they would need to be separate states ideally. Or you set the activeStateCurrentTime to the end and set the anim component speed to -1.