Which type of ladder has flat steps, hinged back, self-supporting, and non-adjustable?

Answer: Step Ladders

In general ladders are with inclined or vertical set of steps or rungs between two upright lengths of metal or wood. Ladders used for climbing up and down.

Step ladders:

It is a self supporting portable ladder, most commonly used in industries. Self-supporting means it does not need any support to lean. So this ladder can be used any where in the rooms. For example middle of the room where support is not available. Also this ladder is non-adjustable flat steps and hinged back.