No. Redmi Y2 is made of industrial grade polycarbonate material.
Yes, Redmi Y2 does have the OTG support.
Yes, Redmi Y2 does have the portrait mode for the rear camera. The front camera does not have the portrait mode.
No. None of the Xiaomi phones comes with the earphone. You have to purchase it separately.
The Xiaomi Redmi Y2 is a slightly better attempt at a selfie-focused smartphone than the model it replaces. It has proven hardware that is capable of delivering a smooth user experience, plus MIUI 9.5 which has a lot of added features.