Ski Safari is similar to Tiny Wings and so it’s probably better to create with either a vector map editor or use procedural generation to create the next part of the level continuously using polygons for the physics collision and overlaying a texture in some manner to represent the terrain. You may want to use renderTexture and/or texture tiling (repeat UV texparams) for the terrain, though I think in Ski Safari it was just a single color or gradient?
I would start by trying to get the physics and collisions correct either using only DEBUG DRAW and adding only physics bodies, or doing that and trying to add a simple solid color from the collision ground line filled to the bottom of the screen.
There’s a few discussions on this.
You can look for cocos2d-iPhone tutorials and try to port them or just use the concepts
This one is really old, so you’d have to migrate source to 3.x
Some iPhone (objectiveC) code for a simple version you could port