Create an object?

Question

Objective-C

Good day, I recently passed a test and there was a question whether there could be a difference in the selection and initialization of an object

SomeClass * object = [SomeClass alloc];
object = [SomeClass init];
// с привычным
SomeClass * object = [[SomeClass alloc]init];

so, sometimes there is a difference, why? point me to an example
PS sorry for my literacy)