With advanced threat detection you can block access to applications via IP ranges (it's touched on briefly here: https://youtu.be/pjGxOXamVfk?t=1209 ).

Advanced threat detection requires an enterprise license. Currently you can't lock a certain user to an IP range, though.

Please feel free to file a feature request with details of this use case if you'd like to see this implemented.

No, this isn't currently possible.

I think that would fall into the threat detection bucket of features we are planning. Feel free to add any notes, comments or suggestions here: https://github.com/FusionAuth/fusionauth-issues/issues/905