Points 1 and two aren't solved in any way, as the buyer has to trust the producer to not lie when making the entry. In other words, the trust problem here occurs before entry into the database.
Point 4 is already solved with by a multitude of companies selling those temperature-sensible stickers (and adding/removing the stickers is the same vulnerability as adding/removing the iot device).
BTW, with a blockchain solution, these are not at all "impossible to alter". That would only be true for a blockchain that is actually decentralized and heavily mined. That implies a blockchain with a multitude of products using the same chain (e.g. not just an OliveOilChain), but then we approach the scaling border very fast, making a blockchain unusable for this use case.