Although not presented in the traditional "jigsaw" format, this is an "alphabetic" puzzle, in the sense that there is exactly one answer starting with each letter of the alphabet. If you'd like the jigsaw version, it is here.

Across:
   7. Snooze fitfully without sulfur gas (5)
   8. Wandering near the city (7)
  10. Classical nickname or a bit inhumane, "Mong" occasionally returns (8)
  11. Woody Allen film and jazz opera contain impromptu classic rock endings (6)
  12. It may help to throw things with the back of the foot (5)
  13. Dietary supplement's claim met with agitation around university (9)
  16. see 28
  17. Strange shtick, getting close to tacky, in retro style (7)
  20. I'm getting married, which is limiting! (9)
  22. Some mixing up Brazilian reserve and river (5)
  24. Empower when a blemish concealed (6)
  26. Alcoholic beverage coming up with evil ends (8)
  27. 50 year old Ripley player's mandible broken by nasty duel (4 3)
  28,16. 200 year old who helped make brewing cleaner, as sour ale is put out (5 7)
Down:
   1. In credo, rot heard: 137 year old Mackellar often quoted by climate skeptics (8)
   2. Love having strange sepia tint around flower (10)
   3. Marvel fabrication, outright smart character in silly cartoon (5)
   4. Hundred year old who created fantastic characters in leanest setting (4 3)
   5. Most of video follows Zambian leader in Ghana for Persian dynasty (9)
   6. Former minister Bailey and future leader stood for election (4)
   9,21. Changes in mini jack, a forty year old money spinner for the music industry (5 5)
  14. Clumsy and full, I slunk about (10)
  15. Target is to include both sides of these, and all in the middle, twice per semester (9)
  18. Royal pot should provide this (8)
  19. Awkward nerd was premier of Victoria (7)
  21. see 9
  23. After he leaves, Ozymandis writer turns and shouts (5)
  25. They are offered at auction, for lots! (4)