For the first, the easiest thing to do is to put square brackets around the item name in the room description – this tells Inform to display the printed name, and since it knows the item’s already been mentioned, it won’t mention it again in the “you san see” line (note that you’ll usually want to make these objects fixed in place so that the description doesn’t stop making sense if the player moves things around – though you can also put if statements in the description to manage this if needed). For the contents of containers, you can make them opaque. And for hidden items, usually the easiest thing is to only move them onscreen once they’re found.
Here’s a simple example that demonstrates some of these techniques – hope it’s clear!
The lab is a room. The description of the lab is "You see a [bunsen burner] and a [lab bench] here. There's also a loose [floorboard] under your feet[if the trapdoor is in the lab]. You've also found a [trapdoor] leading downwards into the gloom[end if]."
The bunsen burner is in the lab. It is fixed in place. The lab bench is an opaque openable container in the lab. It is fixed in place. The goggles are in the lab bench.
The floorboard is in the lab.
The trapdoor is nowhere. It is fixed in place.
instead of taking the floorboard:
If the trapdoor is not in the lab:
Say "You lift the loose floorboard, only to reveal a trapdoor below!";
Now the trapdoor is in the lab;
Otherwise:
Say "You already found the trapdoor."