No, it remains as 8 images.

Magnification indicates how big the viewfinder image is compared to the size of the sensor. So even though the Mark IV will have a much lower magnification factor than the Mark III, the actual viewfinder image will be noticably bigger.

Unfortunately not. This comes with the AC adapter and USB cable to charge the battery in the camera. If you want t a dedicated charger, there is the Olympus BCS-5 Battery Charger linked here. https://bhpho.to/2R5KBTy

NO

Unfortunately, the Olympus OM-D E-M10 Mark IV Mirrorless Camera does not have a microphone input.

All of the OM-D E-M1 cameras have built in Focus Stacking, even my old original MK I.

See Pages 36-39 of the E-M10 Mark IV manual at the following link https://cs.olympus-imaging.jp/en/support/imsg/digicamera/download/manual/omd/man_em10m4_e.pdf

If you are shooting ambient lighting and you set the Olympus OM-D E-M10 Mark IV Mirrorless Camera with 14-42mm Lens and Accessory Kit (Silver) [A] Aperture Mode, you set the lens' aperture setting (and your chosen ISO setting) while the camera sets the shutter speed. The point of the semi-automatic modes (Shutter-Priority and Aperture-Priority) is you select one setting while the camera's light meter selects the other setting while attempting to maintain a proper exposure. As such, adjusting the aperture will only affect your depth-of-field when shooting with ambient lighting. You change your aperture, and the camera changes the shutter speed to keep the same exposure (light level). If you want the exposure to change when changing your aperture, you should be shooting on [M] Manual Mode. In Manual Mode, if you adjust the aperture and nothing else, if the aperture is opened, the exposure will be brighter as more light enters the camera while all other settings stay the same. Conversely, if the aperture is closed, the exposure will be darker as less light enters the camera while all other settings stay the same.