IP i was provided by vercel for my custom domain is by Russia, though I have potential users from there
I see that IP from my default domain with *vercel.app is working and I have a question. Can I somehow request my Ip to be changed?
The domain troubleshooting guide can help with most custom domain configuration issues. You might be able to use that guide to solve it before a human is available to help you. Then you can come back here and share the answer for bonus points.
You can also use v0 to narrow down the possibilities.