Lack of anti-freeze in sub-freezing temperatures. The water in the block freezes and expands.
Antifreeze in the oil of any engine means there is a crack in the head gasket, or worse, in the block.
Yes
Are you talking about a crack in the engine block? Sorry, it's not repairable.
yes
It should not
no
If ice forms anywhere in the engine, it can crack the block.
it is not a cracked engine block it is just a loose block
Most definitely.
crack the engine block and oil mixes with water or antifreeze.
Antifreeze helps by not allowing the coolant to freeze and possibly crack the water passages of the block.
There is no permanent fix for a cracked block except replacement. There are some things that will get you some extra time, but due to the pressure and vibration of an engine nothing lasts and more time causes even more damage.