Re turbulence: in general terms, the certification requirements require that an aircraft can withstand the ‘worst case’ gust (turbulence) from both aerodynamic and structural perspectives when flying at Vra; at slower speeds, a stall (or roll upset) is possible.
I would add that the 'worst case' gust is a certification standard that nature can and does exceed at times, perhaps at the 10^^-9 frequency.