Beside the RESET also are two extra pins, one is IOREF which supports the extension board stand load voltage.
The stitching just shows extension board the current on-board voltage. The other one is backup placeholder pins.
RESET button position is changed, and moved to near the USB interface of voids, which is more convenient.
ATmega16U2 replaced 8U2, but it does not mean that the 16k flash of R3 can make your code run faster.
Type: UNO R3
Color: black + blue
Material: Heavy gold plate
Analog Input Pins: 6
DC Current per I/O Pin: 40 mA
Weight: 27g / 0.95oz
Size: 6.9 * 5.3 * 1.4cm / 2.72 * 2.09 * 0.55in ( L * W * H )
Packing List: C2729
1 * Development board
1 * USB cable (61cm)