Hi Mr.Wood, This is Steven from your 3rd period class. Here are my answers to your questions.
Question1: It looks like there's about 386-388 parts per million of CO2 on the graph.
Question 2:I think the data from on the graph was collected during the day.
Question 3:In two hours, the amount of CO2 should go down. It should go down because the plants would be in the sun even longer, so they would be carrying out photosynthesis longer.
-Steven