iterators can't access problems properly

Question

I am trying to access the element of a vector using the iterator. But I get strange outputs.

std::vector ivec{ 7, 6 , 8, 9} ; 

std::vector

        

Answer 1

As it is stated in here,

Return iterator to end, Returns an iterator referring to the past-the-end element in the vector container.

The past-the-end element is the theoretical element that would follow the last element in the vector. It does not point to any element, and thus shall not be dereferenced.

Because the ranges used by functions of the standard library do not include the element pointed by their closing iterator, this function is often used in combination with vector::begin to specify a range including all the elements in the container.

If the container is empty, this function returns the same as vector::begin.