How does a person inherit this genetic disorder? Is it dominant or recessive? Is it genetic or chromosomal?

This disease is autosomal recessive, which means that both of the parents must pass on the gene for it to affect a child. The parents would both carry one gene, but it would not affect them. However, since XP is caused by the mutation of several different groups of genes, only one of the pairs has to be mutated for a child to have it. It must be both copies of the same group that is mutated though.