No. 4, i.e. Caper Spurge (Euphorbia lathyris) is also known as the 'Mole Plant'. It is said to repel moles - so if you haven't seen any moles, then it must be working :-) I remember being pleased when the plant turned up in previous garden, and though I said 'a bit invasive', that's only by seed - it dies after flowering (in its first or second year), so not difficult to control. One has recently appeared in my present garden.And I said I'd probably learn something: that No. 2 'weedy Euphorbia' is Petty Spurge (Euphorbia peplus). This also dies after flowering, but manages to flower and seed before you've even noticed it - I've never any shortage of seedlings, despite pulling them up when I see them. I think I can see the flowers in your photo, and there's a second sneaky specimen of it at bottom left.