Requirement Dimension in Business Rule

Hi Experts,

I'm in BPC NW 10 and I wanna create Business rule in Financial model to perform an opening balance for next month for account sales.

The Question is :

1. Is AUDIT Type Dimension a mandatory for create a business rule ? Is it enough if i'm only use ACCOUNT and FLOW ( Subtables ) type dimension ?

2. In Dimension FLOW, there are member : Opening, Increase, Decrease. How to setup in business rule ?

3. Do i need create the business rule rule for every month and year ?

Thanks,

Suprapto