Unsigned can hold a larger positive value and no negative value.
Yes.
Unsigned uses the leading bit as a part of the value, while the signed version uses the left-most-bit to identify if the number is positive or negative.
There are different ways of representing signed integers. The easiest to visualise is to use the leftmost bit as a flag (sign and magnitude), but more common is two’s complement. Both are in use in most modern microprocessors — floating point uses sign and magnitude, while integer arithmetic uses two’s complement.
Signed integers can hold both positive and negative numbers.
Yes.