Yes - if you have a half-hourly supply, you must have an MOP contract due to legislation.
Businesses have the option of appointing their own MOP - you do not have to leave it to a supplier default.
None - E for Energy will take care of everything for you.
They will install, maintain, and communicate meter data to ensure that you are billed and reported accurately.
No, only businesses with meters that are half-hourly restaurants or are a maximum demand customer of 100kW+.