Yes it is Euro by default but you can change it to USD if I remember it correctly, its been several months since my last play here so I do not really know if there is a change or not. For the free spins bonus, what you shared here is basically the same issue that I experienced and I have to say it is due to restriction by the game provider. What I did to fix it so I could play the free spins, switching my IP through VPN. Since using VPN is not something prohibitted by Casinopunk as they give VPN recommendation, so you may use it in order to play the FS.
Casinopunkz.io has their tool to detect guest's IP address and if you access the site through Tor with likely IP address from restricted country, after a short time like some first seconds, they will show that you can not access their site.
If they detect it with guests, they will surely do the same with users and I think of what you shared too. The default currency will very likely displayed automaticallly with log in IP address. In some other sites, you can customize it in your account settings and choose a default / favorite fiat currency for your account on that casino.