I've never bought the Sweet & Sour Chicken from Tesco, but used to buy a LOT of their Ready Meals when my Dad was here, as they were fast and convenient, so I didn't have to spend hours cooking, leaving him on his own, which upset him. I always froze them, chicken, beef, lamb, etc and there were instructions for cooking from 'chilled' and 'frozen' on the label. Invest in a magnifying glass for the small print. I use one constantly, now that my eyes are getting worse!
ps ALL the meals I bought were Tesco produce. I buy from them online these days and have it delivered.