Answer to Question 6
This depends on the load intended to be used or connected to the battery bank which is rated in watt-hour or amp-hour.

Answer to Question 7
An inverter is an electro-mechanical device that converts DC (direct current) power from the solar panel into a useable form of AC (alternating current) power. Conversely, it also inverts AC to DC for battery charging. >>>>Click here to view diagram

Answer to Question 8

An inverter performs dual tasks in the sense that the needed AC power is obtained from DC power that is stored in batteries by conversion through the semi-conductor devices in the inverter.
Conversely inverter also perform the function of a charger when an AC source is passed through it, by converting the AC into DC that is used as charging current for batteries.