Yes, Redmi Y2 does have the support for Miracast.
Redmi Y2 comes with a 2A output charger in the box.
No. Redmi Y2 is not a waterproof mobile phone.
Yes, Redmi Y2 does have the fingerprint scanner & face unlock, too.
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.