G3 and G4 do not use the same SoC. G3 has an MSM8916, while G4 has an MSM8952.
Nougat's CTS requires either OpenGL ES 3.1 or Vulkan support. MSM8916 supports neither.
Nougat's CTS requires either OpenGL ES 3.1 or Vulkan support. MSM8916 supports neither.
Particularly, the ending paragraph in 3.3.1 which says that you must export ES 3.1 symbols for linking purposes but their implementation is only compulsory up to the level for which the device declares support.
The following section 3.3.1.1 also mentions that Vulkan libraries and symbols must be present for linking purposes but may report zero VulkanPhysicalDevices.
Additionally, there are several qualcomm releases for 8916 nougat (LA.BR.1.2.9-01310-8x16.0).