I'd suggest reading the company releases, it's all there.
Yes open pit maximises returns but they're being held up with local approvals. They've tried to use a local quarrying firm that have approvals in place but they're holding RFR hostage on price for a rapid start. RFR are confident of their own open pit approval and are willing to pursue the underground option until the open pit operation by them is approved. The time frame to approval for in house open pit mining would appear immaterial.
RFR Price at posting:
8.8¢ Sentiment: Buy Disclosure: Held