Poison bug

Sage Advice: You can check Poison basic rule in Player’s Handbook p.153 that only describes: “…the poison retains potency for 1 minute before drying.” In Dungeon Master’s Guide p.257 some poisons could be very lethal if last for 1 minute (10 rounds).

My advice is that applied poison last until the weapon strikes or 1 minute is passed.

Dash twice

Sage Advice:
Rogue Cunning Action is described in Player’s Handbook p.96
Monk Step of the Wind isin PHB p.78
Bonus Action PHB p.189
Dash PHB p.192