What is the difference between i++ and ++i?

Answer 1

Simplified answer for you.

++x Adds 1 to x's value and then assigns it.
x++ Assigns x's value then adds to x.

int x = 3;
int y = 5;

cout << y;

This outputs y's value of 5.

Now using the increments.

int x = 3;
int y = 5;

y = ++x;

y's previous value is now cleared, and ++x modifies x's value to x+1, then assigns it to y.

cout << y;

It now outputs 4. (x = 4, y = 4)

If it had been y = x++, x's value would have been assigned to y, then x's value would be x+1.

It would output 3. (x = 4, y = 3)

Answer 2

The increment in i will be the same, the difference is in the return value of the statement. Every statement has a return value, and the ; at the end of every sentence is used to tell the compiler to discard it.
++i gives the value of i AFTER adding 1 and i++ gives the FORMER value of i. (¿Or it was the other way around?, I can't recall).
The difference is only noted if you are using this return value for something.
Try
int a = i++;
or
int a = ++i;
In both cases i is incremented by 1, but a would hold a different value.