Do you NEED any of them? Unless you are trying to correct a problem you are experiencing, I.E. something doesn't work, or is not supported by your current BIOS, you don't NEED to update anything. As a general rule you should only update a BIOS to correct an issue you are having, not just to get the "latest & Greatest" BIOS.
That being said, if you ARE going to update your BIOS, then (in your example) going to 1.2 should give you everything that 1.1 had. You should be able to go from 1.0 directly to 1.2 without having to install 1.1.
All firmware updates are images and not patches. They contain the entire firmware code and overwrite the previous firmware completely. Ergo, all firmware updates are cumulative by nature so grabbing the latest one is all you need to do.