In world 1-2 go to the area where the rope is and go to the area below it to the left. The
platform that carries you to the top is next to a lower ledge. Whwen you jump on that
extra ledge you can see a area that Phineas can dig through. Dig through the pile to find
the gold spring and fix the gree platform! The rope is the thing that both Phineas and
Ferb must work together to cross. Don't cross it or you will miss the scraps.

dig in the boxes you find around peoples front yard and back yard houses

How do you get to the last entrance in the factory? I have tried and tried again to find a
way around but i just cant find a way! Have i completely messed up?

When you find Perry the Platypus in the factory, go to the left of the "Scraps Box" near
him and run and jump on to the Moving Belt/Conv. Belt and jump onto the next platform,
then the next belt, then the next platform. Find the ladder on the right and climb it.
Instead of going up the next ladder (Or jumping onto the next platform), keep going right
after you climbed up the first ladder and you will find a computer. Switch to Ferb and fix
it. Then go past the box that was moved and search the "Scraps Box". You will find some
small keys. Use it to fix the doorway and go through it. (And fix the "Elevator Pad" next
to it if you want.) Sorry if I confused you.