Correctness of writing H3C as opposed to CH3 in a carbon chain
Your answer is the same as the book's. The book wrote the first carbon as $\ce{H3C}$ to stress that the chain continues via a carbon to carbon bond, not bonded a carbon to hydrogen to carbon bond.

As for why it's not like this in other examples, technically it is not necessary to write it this way, but it's strange your book lacks that consistency.