Development Environment SharePoint 2010

I have some questions about SharePoint 2010 development environment. I want to develop a solution package.

1. Should development environment is the same version as environment production?


2. If I need external data, like ERP data, SAP data, etc. Should SharePoint first connect to these data base?


3. I am confused about the permisson. Because SharePoint has different permission with ERP/SAP. Should I need an account for these 3 system?

Thank you in very much.