Does anyone have any experience with redeeming AY+ points for hotel vouchers? I did a search and found nothing.

I'm looking at the Finnair Shop website, and for example, a voucher for a serenity room at the St. George can be purchased for 1,000 points + 151€. Similarly, a voucher for a deluxe room at the Hotel Kamp is 1,000 points + 156€. A comfort room at the Lilla Roberts is 1,000 points + 121€. These seem like they could potentially be good deals, depending on dates and season.

1. Are there any restrictions besides the few blackout dates listed on the website (3-5 Dec)?
2. Can the voucher be used as long as any room in the applicable category is available, or are there other restrictions?
3. Is it right to assume that to redeem the voucher you have to call the hotel?
4. Is it also correct to assume that any benefits (through Marriott or Hyatt) are not applicable when using these vouchers?

Thanks in advance.