Proof it by bringing water to the temperature in the instructions on the back. Stir in 1 tsp of sugar and one packet of yeast. After five minutes it should begin to bubble. At the end of 10 minutes, it should have a rounded crown of foam on it. If this happens, yeast is active.
First letter is year, next is month, then year.
CODE will indicate expiration date. First letter is year, next is month, then year. 2nd digit is year, first letter is month, third digit is plant. On first line the last four numbers are the Julian day and last number is year. First number is year, next three are Julian calendar.