Stuck with a delayed OC, what now?

Possession for my 3BHK in VR Developers' Keya Spring was 4 months late, just moved in last month. Honestly, looking back, the builder-buyer agreement felt so one-sided. We took possession without the OC because we couldn't wait. Is that even fully legit? What are the real legal options under RERA for such delays? Did other Keya Spring buyers face this? Wondering if the RERA complaints process is truly effective for compensation, or mostly just on paper.