You don't need to enable VoLTE. Insert the Jio (VoLTE enabled) in any slot. By default, VoLTE will be active. If it is not, you can change the network preferences from Network option in settings.
Alternatively, you can follow a much easier way:
You can check the below video to get more clarity:
Complete specs could be found here: Asus Zenfone Max M1
Yes, Asus Zenfone Max M1 supports OTG. USB OTG or USB On-The-Go is one of the most recent technologies that allows you to connect your pen drives and in some cases hard disks to your smartphones and tablets. It has a cable and through that cable, you can directly view and use your pen drive in your smartphones.
You can find the specs of Asus Zenfone Max M1 here: Asus Zenfone Max M1
Yes, the Asus Zenfone Max Pro M1 does support dual 4G. The 4G Band supported by the device are TD-LTE 2300(band 40), FD-LTE 1800(band 3). These days all the smartphones supprort 4G and VoLTE.
You can also check the complete specs here: Asus Zenfone Max Pro M1
You can easily upgrade your phone with OTA Updates.
For unofficial upgrades, you need to root by unlocking its bootloader, install a recovery and flash a supporting zip along with gaps. XDA Developers is really a helpful site for the process, support, and Custom ROMs.
You can check the full specs here: Asus Zenfone Max M1
Yes, you can play Free Fire on the Asus Zenfone Max M1 as it is an Android v8.0 phone and it comes with the Snapdragon 430 processor with 3GB of RAM.
Check its gameplay-
Check Full Device Specifications Asus Zenfone Max M1
Asus Zenfone Max M1 comes with a massive 4000 mAh battery.
The device does support quick charging and also provides quite impressive battery backup.
The device easily swifts through a whole day of heavy usage and still leaves you with a neat margin for optimum use.
You could also check out other detailed features related to Asus Zenfone Max M11 here.
Asus Zenfone Max M1 does not offer Gyroscope sensor in its physical specification.
It is quite surprising to have other sensors such as Fingerprint (rear-mounted), accelerometer, proximity, compass but not Gyroscope.
However, it is to be kept in mind that it is a budget flagship device and may not have this sensor for the reason of cost cutting.
In the meantime, do not forget to check all the detailed specifications and other updates about the device here.