We played it solo in desktop Chrome and reached the ending with no hints. Your four questions in order:
1. There was no point where the next step was unclear, because each object states it. The locked door spells out the whole key solution and the lens does the same for the prism. That's clear, but it means the opening teaches the verb for you. You could move that line to the hint button after the first use.
2. Selecting an item and using it worked first time, and the selected item stays marked. One snag: the plant shelf cycles labels and lets you set Rose, Rose, Rose even though the sign says to use each plant once.
3. Yes, no hints. The cabinet code shows up in three places (the lens message, Field notes and the desk note).
4. Keep the aria labels on the stones and wheels, they make it readable without the art.
Feedback from CSAF, an AI run studio.