nohi bus from takayama to shirakawago

We will be going to Shirakawago on 9th Jan and intend to buy the 5 day Hokuriku Pass.

1) Can I call nohi bus company to reserve seats on the bus before I buy the 5 day pass or do I need the pass before I can reserve seats?

2) Will I be left stranded in Shirakawago if there are no more seats left in the bus ? Will the bus company allow passengers to get up the bus even though there are no more seats left in the bus ?

Here's answer for your question 1):

œ Users of the SHORYUDO Bus Pass cannot make reservations in advance by internet or telephone for buses that require a reservation.
œ Tickets Number ❶ (From the Airport out-bound), Tickets Number ❶-2 (From Nagoya out-bound), and Tickets Number ❸ (To the Airport inbound) can be used with a condition that the pass will be used within the validity period of each course.
œ Present the SHORYUDO Bus Pass at the ticket window of the bus company (see ticket information centers on page 3) to reserve a seat. A
reserved seat ticket will be issued. If the bus is at capacity, it will not be possible to ride it. ¦Some buses do not require reservations.
œ When getting on the bus, show the SHORYUDO Bus Pass and the reserved seat ticket to the bus driver.
œ When getting on the bus, show the SHORYUDO Bus Pass to the bus driver. The driver will collect the reserved seat ticket.
œ At bus stops that have no ticket window with a clerk, pass holders may ride any bus with an empty seat. Show the driver the SHORYUDO
Bus Pass when boarding the bus

PLEASE BE NOTED THERE ARE SOME NON RESERVED SEATS BUSES WHICH IS RECOMMENDED TO SHORYUDO BUS PASS HOLDERS.

Regarding your question 2), they will operate extra buses in case of full on the day if it's non reserved bus.

For further references, you may refer to the website below:
mwt.co.jp/shoryudo/instruction_en.pdf.