Exhaust of an engine is a gas.
Internal engine antifreeze leak what else could cause besides headgasket? there is no antifreeze in the oil it is clean
Exhaust leaks close to the engine.
Sorry to tell you but white smoke from the exhaust is caused by coolant entering the combustion chamber. You have a blown head gasket. STOP driving this vehicle or you will destroy the engine.
Moisture in the exhaust, or a cold running engine.
The engine is burning fuel.
An exhaust restiction, like a clogged catalytic convertor
Yes, a prolonged exhaust leak will eventually cause problems with your cylinder head. The leaking exhaust is very hot and you can cause small cracks in the head if you don't repair the problem promptly. If you can hear the exhaust leaking, it may already be too late! Get it checked out soon!
From the intake, yes. From the exhaust, unlikely.
Yes, if it is leaking or if when it was replaced, oil leaked onto the exhaust or exhaust manifold.