Change Name field format

[Harald]

Is it possible to change the Name field from Firstname Lastname to Lastname Firstname format after the import?

[tanya]

you can set this format in import settings.
If you imported data, you can edit this is with workflow. Or revert import and Import again with fixed settings

[Harald]

Can I change the displayed sorting to Lastname Firstname?

[tanya]

only with developing. You need to override person name field