Unix files have two kinds of ownership: user and group, each with its own permissions. Normally, the owner of a file should have full access to it, whereas members of a work group to which the owner belongs might have limited access, and everyone else, even less access. This last category is called other in Unix documentation.
For a file,
are the permissions for its work group necessarily permissions of its user owner?
Since its user owner is a member of its work group, I guess the answer is yes, unless its work group excludes its user owner in the case of permissions. The permissions of its user owner may be more than those of its work group.
are the permissions for its user owner necessarily permissions of other?
Some said 'other' means the entire world. In that sense its work group should be a subset of 'other', so I guess the answer is yes, unless 'other' excludes its work group. The permissions of its work group may be more than those of 'other'.
If it matters, I am focusing on Linux.