If you consider qualities to be unique, make sure you choose the
Fruits Bat Cave as Salmonberry of higher qualities is only possible there. There are a few other "gotchas" that may no longer be possible or exploits some glitch but if you are interested, I have a list of them:
Mermaid's Pendant | Multiplayer clone glitch the limited item to get a spare |
Qi Fruit | Exploit from buying and reselling to Pierre's (pre-1.6) |
Advanced TV Remote | Multiplayer clone glitch the limited item to get a spare |
Arctic Shard | Multiplayer clone glitch the limited item to get a spare |
Berry Basket | Multiplayer clone glitch the limited item to get a spare |
Pierre's Stocklist | Do not give Pierre the item |
Gourmet Tomato Salt | Multiplayer clone glitch the limited item to get a spare |
Lost Axe | Multiplayer clone glitch the limited item to get a spare |
Lucky Purple Shorts | Multiplayer clone glitch the limited item to get a spare |
Ornate Necklace | Multiplayer clone glitch the limited item to get a spare |
Pirate's Locket | Multiplayer clone glitch the limited item to get a spare |
Stardew Valley Rose | Multiplayer clone glitch the limited item to get a spare |
Trimmed Lucky Purple Shorts | Multiplayer clone glitch the limited item to get a spare, no longer true as you can get multiple of Lewis' pants |
War Memento | Multiplayer clone glitch the limited item to get a spare |
Wriggling Worm | Multiplayer clone glitch the limited item to get a spare |
Strange Capsule | Multiplayer clone glitch the limited item to get a spare before it turns |
Weeds | From chopping down mushroom trees (pre-1.4) |
Stardrop | Taken into inventory from Museum's (pre-1.3.27) |
Seaweed (Silver, Gold, Iridium) | Forage at beach (pre-1.6) |
Salmonberry (Silver, Gold, Iridium) | Fruit Bat Cave |
Journal Scrap | Multiplayer clone glitch the limited item to get a spare (although after 1.6, the behavior of the cloned journals and secret notes changed completely - it no longer duplicates the text of the original journal/note, but now do nothing) |
Secret Note | Multiplayer clone glitch the limited item to get a spare |
I also have to correct that part about 14 heart event (at least on the switch), having done Penny's three times already.
It is indeed once per player profile, and in fact you can do more than 3 on the same save if you delete the profile and create a new farm help - indefinitely. I've actually triggered Emily's twice as well because I needed Emily's Boots and the custom tailored version of it as well.
Here's a list of items (attached and created by me for latest Switch version, so may not be complete as I did not delve into the code) for reference if you would like to match with mine. I can't attach my Excel sheet so unfortunately this text file doesn't show which item qualities each item is available for.