Reusing assets is acceptable only if the game is free, or a homebrew, and definitely not if it's ON STEAM.
It's supposed to be a professional game if it makes it to those platforms. Can't be going around ripping off stuff.
Those orange blocks are totally from CVIII's first stage. The forest wood could arguably count as well (though it may have been edited).
I say this as someone who often uses assets from other games (though my sprites are usually my own).