Gionee A1 Plus is a fully metal body phone and it does support fast charging, too. Besides, it has huge 4550 mAh battery. So, you may notice a minor heat issue while charging the same but otherwise there were no heat issues reported during our review.
Yes, Gionee A1 Plus is a true 4G VoLTE mobile phone and you can use VoLTE without any problem.
Gionee A1 Plus has dual sim card slot of different size. You can use one micro sized sim card and another nano size sim card in this phone.
Yes, Gionee A1 Plus does support OTG.