SAF Levy was introduced to immigration last year, this is a fund which contributes to the training of Australian Citizens & Permanent Residents whilst hiring foreign employees. This is a required fee to be paid by sponsors only.
Once your 186 visa is granted, you have full permanent residency rights and therefore have no enforceable obligation that prevents you from changing your employer or your role. However your employer has right and obligation to inform Immigration department about it and that can start further investigation. If you visa is not granted yet, changing employer will mean new nomination [...]
Yes, 186 visa it is permanent visa. Once granted, it allows the holder (and any family members included in the application) to: stay in Australia indefinitely.