Code snippets helps you to break the permission inheritance in SharePoint for the list, list item and subsite.
In this post, I will show you have to get the permission level for the Groups associated to the Web Site Level using the Managed Client Object Model. Managed Client Object Model – Get Permission Levels associated with all Groups
If the user want to choose cascade or Restrict option for the lookup field, that user must have the ManageLists permission for the Lookup List. To View the list of Permissions, check the SPBasePermissions enumeration.