Another beginner question

I'd been using Forest Snare to immobilise various monsters (which ones is largely irrelevant) but even though they cannot attack the rulebook says to deal a shadow card to every monster engaged with the player, do I have to deal and resolve one for creature's affected by Forest Snare?

If yes then this led to one instance where a shadow effect in another attack asked me to discard one attachment I controlled and, as it was my only attachment, I removed the Forest Snare from the other monster. Does this monster then get it's full attack? Because I assumed it could not attack then I had not been dealing it shadow cards that could have been resolved each round.

Let's say I had been dealing a shadow card to a creature affected by Forest Snare, each round I don't assign it a defender and then reveal the shadow card expecting a null attack. shadow effect asks me to remove an attachment and I have to get rid of the Forest Snare on it. Because shadow effect resolution comes before the attack resolution but after defender assignation then assumedly this monster gets a free undefended hit on me? I guess that's the surprise of the fiendish shadow cards!

How should I be playing this situation? Should I be dealing and resolving shadow cards on creatures that are engaged but unable to attack? If a creature has it's Forest Snare removed by a shadow card in another attack then presumably (as combats are resolved one by one) I would still have the option to assign it a defender?

Also just another small one, cards that have a "when revealed" effect don't occur when used they appear as shadow cards, correct?

Thanks guys

You are correct that each enemy with which you are engaged is dealt a shadow card at the beginning of the combat page (see rulebook pg 18). If your forest snare holds then the you do not assign any defenders to that enemy and at the end of your attack phase all shadow cards are discarded (see rulebook pg 20). If for reason due to another attack you were forced to discard that attachment from play you would have to assign a defender as you normally would.

Related to your other question, only shadow effects have any bearing when the enounter card is dealt as a shadow card. All other text, including when revealed text, is ignored.