There is something about portals here: [url]Portal]
But basically the idea is when you enter in a portal (collides with it), set the position = other portal position.
And here are some words about random objects: [url]Display random object on screen.]
Also, if the collectable objects are simple things like different fruits to give points, instead multiple objects you could use a single fruit object with multiple animations, and choose a random animation when you create it.