Daisy, 
#3

- If by translating in Zanata editor (po/pot files conversion, push to Zanata, translate in editor, and pull po file, convert to the original file format), then yes. You can see comments in the editor.

- If by using our new glossary user interface in Zanata 3.8 (http://docs.zanata.org/en/release/user-guide/glossary/edit-glossaries/), you can see the comments along side with the translation.

#6 - this can be done only if glossary is being translated in Zanata editor. (po/pot files conversion, push to Zanata, translate in editor, and pull po file, convert to the original file format)