Nagoya 1 week Itinerary advise

Goo day everyone, I am planning my first time travel solo in Japan on Feb 17-24, 2019.
I would like to ask some advises on my itinerary
Planning to buy Shoryudo 3 Day Takayama Bus Pass (Haven�ft buy yet)

Feb 17 – Sun
Arrive at Chubu Airport (Night time)
Check in Hostel in Nagoya

Feb 18 – Mon
Exchange for Physical Pass and Reserve bus slot to Takayama and return at Nagoya Station
Inuyama Castle
Sakae area (Oasis 21 and other Mall)
Nagoya TV Tower

Feb 19 – Tue
Check Out Hostel in Nagoya
Bus to Takayama (1st day of Bus Pass)
Reserve bus slot for Shirakawago and return
Old Town
Takayama Museum of History
Higashiyama Walking Trail
Check In Hostel in Takayama

Feb 20 – Wed
Shirakawago

Feb 21 – Thu
Takayama Morning Market
Check Out Hostel in Takayama
Bus to Nagoya (Noon)
Check in Hotel near Nagoya Station
Osu Kannon Temple and Shopping Arcade
Sakae Area

Feb 22 – Fri
Legoland and Nagoya Sealife

Feb 23 – Sat
Check Out Hostel
Nagoya Castle
Nagoya Station
Depart at Chubu Airport (Night time)

Do you think I can get the earlier bus ride to Takayama and Shirakawago in this Itinerary? Or should I reserve online for the bus trip (more expensive)?
Is 4hrs in Shirakawago is too much? Main objective are Gassho houses, Viewpoint and Snow
Any idea regarding the temperature during time? I am coming from south east asia country

For Feb 18, you are missing the crown jewel of the region - Meiji Mura. Inuyama Castle is one of the few surviving originals, but not that impressive. Meiji Mura though is really the finest open air museum in Japan and you should definitely add it - skip Inuyama Castle if you have to.
For Feb 19, one of the best places in Takayama is the HIda-Takayama Folk Museum - very much like Shirakawago though nobody lives in the buildings and you can leisurely explore them all. As for Shirakawago on Feb 20, it only takes a couple of hours to see it, unless you want to add the other villages like Gokayama.

Thank you Ken for the Inputs. I may consider Meiji Mura.
Is it possible to see all of Meiji Mura building without buying the unlimited ride?