3 and 4 are definitely a milkweed of some kind. My guess is that it's the one called "Hairy Balls" by some seed companies here in the states--for the round inflated seed pods--or "Swan Plant" elsewhere as Medbury pointed out. Thanks for posing the question--I'd never seen photos of the flowers before; they're really quite handsome!
See if your flowers and plant look like these:
http://www.metafro.be/prelude/prelud...ysocarpus3.jpg
http://www.flickr.com/photos/vlashton/2048186369/