Complex sentence: The Prix Jean Prat for older horses was renamed the Prix Vicomtesse Vigier in 1985, and at this point the version for three-year-olds was promoted to Group 1 status.
Split into simpler sentences: The Prix Jean Prat for older horses was given a new title in 1985--the Prix Vicomtesse Vigier. The version for three-year-olds retained the name Prix Jean Prat, and it was promoted to Group 1 status.