No. You cannot record 4K videos from the Nokia 2.
No. Nokia 2 does not have the front camera flash but it does have the BSI sensor, which helps to take excellent pictures even during low light conditions.
No. Nokia 2 comes with non-removable 4100 mAh battery.
Yes, Nokia 2 does have the OTG support.
It's not a bad phone, this Nokia 2. It's just that there's only so much you can do within a budget this tight.