1. The first one is possible by pressing a add-on icon in toolbar and choosing "Update URL"
2. It is currently impossible. There is an opened issue: https://bugzilla.mozilla.org/show_bug.cgi?id=1419195

> ad1 not work - URL changing but the labels disappear
I cant reproduce your case. Provide me with a sample:
a) bookmark data (title, URL )
b) URL of page you are trying to update from

Reply2
I understand now what you meant.
At this moment it is impossible as well. It is not my fault:
https://bugzilla.mozilla.org/show_bug.cgi?id=1225916
After testing I found that tags are cleared when url is updated. Updating a title only keeps tags untouched.