Your questions and numbering system is a little confusing. I hope I answer the indicated questions.
1. A motherboard has less effect on overall systems performance than either the CPU or CPU. From that perspective it will be better to buy a stronger GPU (graphics card) and a motherboard with an older (that would be the B85) chipset. In case language difficulties intervene, I recommend you buy the Sapphire R9 280 Dual-X.
For your CPU you do not have to buy a z-series (the Z97) chipset. Z-series chipsets are for overclocking. You will be best served by an H-series chipset. In order of desirability, choose first a H79, then H77, then an older H- chipset motherboard.
If you buy a H97 chipset motherboard, you can probably use it (with some suture firmware upgrades) for up to Broadwell processors. It will NOT allow you to overclock - for that you will need the Z-series chipset.
Overclocking is dependent on BOTH the motherboard AND the CPU used. You can really only overclock if your CPU is unlocked and the motherboard BIOS firmware supports overclocking.
Finally, there will be a huge and noticeable increase in performance from the R7 256 to the R9 280.