What most people refer to as "invalid" orders are defined in the rules as "unfollowable" orders. I might dedicate a terms section to order types, but the terms are getting a bit clustered despite my attempt at organization.
An order can be overridden by anything the warden says afterwards, including setting ARs. All orders are expected to be continuously followed until the warden says something to override it though (so "get on the line" means don't leave until an order makes you).
So would the example given (Get on beds | Beds AR) prevent a freeday? I remember asking Crown a while ago and in the example I gave (Leaving cells AR | At 9 go to line), he said that would prevent a freeday. Not sure if Crown changed his mind or if the second example applies to the first. Would really like clarification :I