This puzzle is based on the framework described here: Controlling a robot blindfolded on a 9x9 grid
Here is a quick summary. A robot is located somewhere on a grid, but you cannot see it. You can send commands to the robot to make it move one cell left, right, up or down. Some cells can be walls. If a robot hits a wall it stays in its current cell. Your task is to guide the robot to the target cell. Once the robot reaches the target, the game will terminate immediately.
It turns out that any map (where the target is reachable) can be solved with a finite number of commands. Furthermore there exists a sequence of commands that will solve ANY 2x2 grid, no matter where the robot starts, or where the target cell is or where the walls are (including walls inside the grid). What is the shortest such sequence of commands?