A technical report describing Signalling, Backward Compatibility and Display Adaptation for HDR/WCG Video Coding. This report complements and extends work in another report, "Conversion and Coding Practices for HDR/WCG Y′CbCr 4:2:0 Video with PQ Transfer Characteristics". Specifically, this report expands on the application of ICtCp, HLG, and SEI messages in the coding of high dynamic range and wide colour gamut (HDR/WCG) video.