Current (C) means no cutoff; Unavailable (U) means no visas authorized. A priority date must be strictly earlier than a dated cutoff. Employment tables cover EB-1, EB-2, EB-3, other workers, and EB-5 unreserved. Family tables cover F1, F2A, F2B, F3 and F4.
Retrogression is a cutoff moving backward. A priority date that met an earlier cutoff may no longer meet the new one. Current means no cutoff applies; Unavailable means no visas are authorized for that category in that bulletin.
Does Dates for Filing mean I can file I-485?
Not by itself. USCIS selects the permitted adjustment-of-status chart each month, separately for employment and family preferences. Follow the official monthly selection and all other eligibility requirements.