Kanazawa to osaka by thunderbird

1) can I buy ticket from station
2) where is boarding station in Kanazawa
3) where is arriving station in Osaka
4) can I just go and buy the unreserved seat on the spot on the day itself

1)
Yes, order at ticket office faster than ticket vending machine.
https://youtu.be/DCrM4nIs9ns
This is Kanazawa stn's counter.
http://ihoku.jp/wp-content/uploads/2014/11/IHK_7727.jpg

2)
Watch dep info board at ticket gate.
http://ihoku.jp/wp-content/uploads/2013/01/IMG_2418.jpg
From No.2 platform most and a few trains from No.1.
https://www.jr-odekake.net/eki/premises.php?id=0541449

3)
To No.3 platform most maybe.
https://www.jr-odekake.net/eki/premises.php?id=0610130

4)
Why not? But crowded or not depends on travel date and time.

3) Shin-Osaka, then Osaka.