1) Enable XMP in the BIOS.
2) No. Turbo clocks don't apply to all cores. The first core gets boosted to the full turbo clock, second core gets 100MHz less, third gets 100MHz less than second etc. Running all cores at 3.9GHz would require manual configuration, which you can only do on Z170 boards (and ideally an unlocked CPU but with some compromises you can use the unofficial overclocking BIOS of many boards).