Recently installed a 20 amp shared neutral circuit. One leg was 6 GFI receptacles, the other
8 lampholders with 13 amp Fluorescent lamps. Another 20 amp circuit had 5 4 foot (2) lamp cold weather fluorescent fixtures. Q1 Any code violations?

Q2 Do they make a double GFI CB with a shared neutral so I could have eliminated GFI receptacles?

Q3 Could I have combines 8 lampholders and 5 fixtures?

Yes most brands of panels make a two pole GFI breaker rated 120/240 that can handle a shared neutral for two circuits.

The fixtures and lamps can be combined on one circuit, as long as the totla load does not exceed 16 amps.