Advice on Hokuriku region in Nov/Dec

Hi, I'm planning for a tour in Nov/Dec this year. I've a draft itinerary but would like to hear more opinions before finalising it.

Kamikochi & Tateyama Alpine Route - Will they be closed earlier than scheduled (Nov 15 & Nov 30 respectively)?

Kamikochi - No access to entire area after Nov 15?

Kurobe gorge train - Do we need to book for return ride when we get off halfway? Also, is there a need to book the tickets in advance? Will we be taking a high risk of tickets being sold out if we buy on the day itself?

Shirakawa-go, Kenrokuen & Shogawa gorge - When will we see them covered with snow, like in those postcard-like photos? Is there not enough snow in early Dec? How about mid Dec?

Snow activities - Too early in early Dec with not enough snow?

Matsumoto-jo & Tonami tulip park - Are they worth going? How is Matsumoto-jo compared to Kumamoto-jo?

(this is in Tohoku though...)
Mt Zao - How to access it from sendai? Which stop do we alight at? What time is good to see snow monsters?

Appreciate any help given. Thanks!

Kamikochi & Tateyama Alpine Route - Will they be closed earlier than scheduled (Nov 15 & Nov 30 respectively)?

No. They usually get closed as scheduled.

Kamikochi - No access to entire area after Nov 15?

In theory, you could still walk there.

Shirakawa-go, Kenrokuen & Shogawa gorge - When will we see them covered with snow, like in those postcard-like photos?

Ogimachi in Shirakawago usually sees the first snow around early December.

Is there not enough snow in early Dec? How about mid Dec?

It depends on the year. Sometimes, there is no snow, sometimes there is already a lot of snow. In mid December, chances for snow are naturally higher.

Snow activities - Too early in early Dec with not enough snow?

Many ski resorts in the mountains of Nagano and Niigata open by early December.

Matsumoto-jo & Tonami tulip park - Are they worth going? How is Matsumoto-jo compared to Kumamoto-jo?

Matsumotojo is Japan's second most beautiful castle in my opinion. And it is an "original castle". Kumamotojo is a reconstruction. Lacking the original interior, I find it considerably less impressive than Matsumotojo. But among the reconstructions, it is one of the most beautiful. Furthermore, the walls around Kumamotojo are impressive, while Matsumotojo just stands on the plain, surrounded by simple moats.

Mt Zao - How to access it from sendai?

By direct bus or by train and bus via Yamagata.

What time is good to see snow monsters?

Mid February is the best time to see the snow monsters. But due to global warming, the monsters are suffering. In 2009, the weather was too mild for the trees to fully develop into their monster form. They remained snow covered trees rather than turning into monsters (the sight was still nice, though). Hopefully, next winter will be colder again.

Uji, you're practically a live encyclopedia! Thanks so much on the info! It really helped a lot on my planning. I like Kumamoto-jo and thought if Matsumoto-jo is not as good, I'll skip it. Now I decided to keep it in my itinerary. I'm little worried about visiting too many castles, just like too many shrines & temples in Kyoto. All are great but I was too greedy to see as many as I could in my last trip. But some are impressive. like Sanjusangendo, Byodo-in. Thanks!