Can I use Limited Express train for free or I have to pay extra for fast train ?You have to pay the limited express fee separately. The slower trains can be used without supplement.
I read, that I have to reserve a seat for Nankai train to Koyasan. Is this right and can I do it before I leave at same day or I have to do it in advance ?
Only the limited express trains require seat reservations. For the others, it is not possible. Seat reservations can be made right until departure. On very busy days, there is a risk that the train books out, in which case it is recommended to make reservations in advance.