Activate grid snapping on C2
On some points place a sprite you can name "node"
create 4 boolean insance variable named 'E' 'S' 'W' 'N' (for East, South, West and North)
For each node you have to manually set the following:
if you can go right set E to true, else false
if you can go down set S to true, else false
if you can go left set W to true, else false
if you can go up set N to true, else false
Then each time your player character is on a node, and you push an arrow key, check if the node allows you to go that way, if yes, start moving the character and disable control until it reaches the next node.
(setting things with the snap feature enabled help to have things properly aligned)
Now for levels, you can add a second instance variable named 'level' which can old text. You set it for each node to nothing if shouldn't lead to a level, else you set it to the layout name holding your level.
And then if the player character is on a node (not moving) and the player hit the "enter the level" control, AND node.level is not equal to nothing, then go to layout (by name) node.level