This might be a repeat thread so sorry ahead of time if it is, but I created a video on how to get to the knife room on community pool.
The rooms provide a player with a knife that is 1 hit kill, which is bad if a T gets it and some T don't have a point shop upgrade on 1 hit kill for their own knife.
http://www.seriousgmod.com/threads/map-secrets.16338/page-2 this is a link I found on the forums it has the secret knife for datmap
That was for the original datmap, I believe the current version has an extra step that involves placing an item into the bin near the traitor room in the main area. As far as order goes I don't have the slightest clue.
I just did it on single player it did not seem like there was some sort of order, but I could be wrong
I am pretty sure we use an edited verison of Datmap and 67th way that prevents you from getting the Knife for various exploit reasons. Could be wrong, but I have never seen anyone have the secret knife on either of these maps.
I am making videos of the secret knifes currently and I plan on posting them on a new, updated thread soon.