>>11879270I'm going off of memory here so I'm not 100% but I think that room above the save point in the upper left corner of the map has a blue door in it so you should be able to go left from there.
If you go back to the clock room with the double jump or bat ability you can walk in and out of the room and eventually the statue on the left hand side will move and you can jump up the opening to reach a new area
On the right hand side of the map after you go down the long vertical shaft and head right towards the save room if you drop down to the bottom left corner of the vertical room just to the left of the save point, there's a breakable wall that leads to a secret area