Nagoya to Shirakawago

Are there 2 different timing for the bus from Nagoya to Shirakawago?

http://www.gifubus.co.jp/noriai/index.html

Is it highly recommended to book the tickets online in advance?

Which station should I alight? the last or 2nd last station? thanks!!

Highway buses connecting Nagoya City and Shirakawa-go are operated by Gifu Bus, and two buses are scheduled every day to depart at 09:00 and at 11:00 from Meitetsu Bus Center (Bus Stop No. 7 on the 3rd floor) in Nagoya City.
(Your hyperlink is for the webpage of Gifu Bus concerning ordinary route buses, not highway buses.)
The one-way highway bus ride to Shirakawa-go bus stop (= the second last stop) lasts for about 2 and a half to 3 hours. The one-way bus fare is 3600 yen.
You can try booking this bus (and the return bus) on the phone, which is recommended, from one month before the boarding date.
(If you hope to pay the bus fare in cash on that day in your bus, you can try booking the bus but you cannot designate your seat.)

There are more connections via Takayama City between Nagoya City and Shirakawa-go.
Your options to travel from Nagoya City to Takayama City are explained in a japan-guide.com webpage.
http://www.japan-guide.com/e/e5908.html?aFROM=2155_5900
Nohi Bus and Hokutetsu [Hokuriku Railroad] are co-operating highway buses between Takayama City and Shirakawa-go. The timetables in English language are available also on this japan-guide.com website.
http://www.japan-guide.com/bus/shirakawago.html

Thanks omotenashi san. I am taking the highway bus from nagoya to shirakawago.

Would you know the mode of transport available between hirase onsen and shirakawago? I should be staying near hirase onsen and need to travel between the farmhouse and tourist attraction.
Any recommended farmhouse please?

Are there frequent buses around that area? Or taxi?