According to Osho, to tell imagination from authentic past-life recall, look for two signatures: stability and direction. Genuine recall is a 'closed chapter' that reappears identically each time and unfolds in reverse—beginning with death and moving back through events to birth (and earlier). Imagination moves forward from birth to death, shifts details across sittings, and cannot be replicated exactly.
Real past-life memories always replay the same and run backward from death to birth; imagination runs forward and keeps changing.