Yes, the hardware of Honor Holly 3 does support upgrade to Android Nougat. However, the company has not yet published any OTA Software Update for the same.
Yes, Honor Holly 3 is a true 4G VoLTE mobile phone.
Honor Holly 3 comes with 5.5 Inch HD IPS display which is excellent to use under direct sunlight, too. The display has an aspect ratio of 16:9 which is ideal to watch movies or playing games. Honor Holly 3 supports 16 million colors reproduction. The display is made of highly toughened aluminosilicate glass, which is almost 3 times tougher than the regular display glass. The contrast ratio is of 1000:1.