I agree with your answer for Compound B. It is, in fact, methylidenecyclohexane. When terminal alkenes are treated with acidic KMnO4, it gives of CO2 as a by-product.
For Compound A, however, seeing as both compounds are just isomers, and the degree of unsaturation for both A and B are 2, the structure you proposed might have deviated from the information given. I suspect compound A to be 3-methylcyclohexene. The first part of question number 2 is somewhat vague, for me, that is, but I just thought of it this way: Compound A reacts with 1 mole equivalent of H2, and when Compound A (the stock solution) is treated with acidic KMnO4, the ring opens up and that the unsaturation is the site of cleavage. That's just what I think, though...