What do you prefer?
I find guessing what you can and cannot do with an object to be too much of a hassle, but then again viewing a full list of things you can do with an object ruins part of the fun. Which is why I cannot decide which route should I take.

I like both. I don't know.

I usually put clues (that are pretty obvious) in the description of that object. Likewise I put clues in room and/or other object description.

When I play games I often find myself just clicking nouns for clues. When I do this, it is largely because it’s a poorly written game. So... in short, typing is preferred but ONLY in well-written games.

I write in squiffy and my games are pretty huge. I don't have time to let people click down through links they can't use, then validate them. For example, if you need a cash to buy something, I won't present the buy link if you don't have cash. I never noticed it to make a difference - most people can figure out they can't buy with no money. And if it was an issue, I'd add text to the description "The merchant frowns at your empty purse" or some such stuff.