1 and 3 are both Chickweed.

Get those Chickweed out before they go to seed if some have not already.

what would be best spray to take out chickweed?

A broadleaf herbicide should take care of them.

Edit: try Weed B Gon Chickweed Clover and Oxalis.

If there is an independent garden center serving your area ask for suitable products there. Take examples of the weeds you want to be rid of with you.

can I use this even after it has gone to seed?

thank you!

Not sure of your location, but pre em for crabgrass in a few weeks from now seems pretty past due.....

You can use it after the chickweed has gone to seed but it will only kill the plants, not the seeds. You'll need to eradicate the subsequent offspring, by what ever method you choose, possibly several times if seeding has been going on for some time. How big is the area? Is it impossible to set aside some time and methodically pull the plants out?

Pre-emergent will take care of the seeds. You will want to have pre-emergent down this fall and through winter, your soil is probably loaded with seed.