4k screen can handle 60hz 90° rotated, but not in 0°
Your model MacBook Pro has an Intel Iris 5100 GPU that uses up to 1.5 GB of your main RAM as its graphics memory. It supports an HDMI-compatible device, including 4K, while using one Thunderbolt display, or supports two Thunderbolt displays. 

In terms of external resolution, officially your Mac can display up to 2560x1600 pixels (using Thunderbolt) or up to 3840x2160 pixels at 30Hz or 4096x2160 pixels at 24Hz (using HDMI). This is why you're being limited to the choices you're getting.