I have a Creative world hosted with a server company but cannot access some of the items in the inventory such as different colored fences, rails, powered rails and cannot spawn sheep, wolves, and cows. Are they running an old version of Pocketmine? is there a list of which items in the Creative inventory still can not be used in the latest version?
Colored fences should have been fixed in a recent development build. Rails/Minecart physics are not implemented yet, so they disallow using them. For entities, you can't use them because entity AI is not implemented yet. They tried implementing that with zombies, and as @shoghicp said, "it was a failure".