Hi,
We have checked for both the issues on our system and it can't be found. Please make sure following-
1. For backend login, please make sure Registration Menu is assigned to only client category not seller category.
2. Permissions for seller should not be enabled as Shop owner. Please reset to default for seller.
Follow this documentation for permissions:
https://www.sellacious.com/documentation-v2#/learn/settings/permission
If the issue still exist pls let us know on live chat.
Thanks