Alpine-Takayama-Matsumoto Area Tourist Pass

Please help to confirm if my understanding is correct:

1) This ticket is being sold only 3 months before the desired travel date. (travelling on May, can purchase on February)

2) only TRAINS can be used but not BUS

3) Is Chubu airport to Nagoya station as well as other in city Nagoya also covered by this?

Check out the information here.
https://touristpass.jp/en/alpine/?utm_source=global.jr-central.co.jp%2...
Japanese version
https://railway.jr-central.co.jp/tickets/otoku_tateyamakurobe/
1) I don't know.
Click on Book Now under Get Your Pass on this link and you can book once it becomes searchable.
It seems that reservations can be made up to one month before boarding (from 10:00 on the same day of the previous month).
https://touristpass.jp/en/alpine/?utm_source=global.jr-central.co.jp%2...
If you buy via travel agent outside Japan, they might be able to tell you if you ask.
https://touristpass.jp/en/purchase/
2) Buses and trolleybuses within the Alpine Route are available.
3) Not covered.
Stopovers are not allowed between Nagoya and Gifu, or between Nagoya and Nakatsugawa.
I think it's easier to get around Nagoya by subway.
https://www.kotsu.city.nagoya.jp/en/pc/TICKET/TRP0001071.htm

Any pass like this one that requires an exchange voucher normally is only valid for 3 months / 90 days.

So yes only purchase you exchange voucher no earlier than 3 months out from date that you can exchange it.