First part is Diels Alder: Diene and Dienophile join (w. heat) to create a cycloalkene ring. You got this part right?
Second Part is easy. Recall that when you add Water and acid (H+) (also represented by H30+)to any acyl compound you convert into a carboxylic acid. This holds true for Acid Chloride, Anhydrides, Esters, and Amides and Carboylate. Adding H30+ to any of these will convert it to a carboxylic acid. The trick to this one is to be familiar with the mechanism (don't panic it's very broad). It's nucleophilic acyl substitution. What that means is that you have an acyl compound(which is nothing more than a carbonyl compound with a leaving group (mentioned above)).
So there are two substitutions with H3O+. The first generates one COOH group and a carboxylate (leaving group of first substitution). Then adding H30+ across the carboxylate forms the second carboxylic acid.
Remember that the dbl bond C==O bond doesn't change for either anyhydride. The leaving groups only changed. They are replaced with OH.
I hope this didn't mess you up. It's hard to explain Ochem in words. Just remember any time you add H3O+ to any acyl compound you will always get a carboxylic acid.
