Not using some segments of RTW ticket
I have a half used CRTW ticket, with a HKG-SIN-BOM-LHR segment left. I am not finding availability on the days I want HKG-SIN-BOM (one or other sectors waitlisted with SQ). The ticket is expiring in a few weeks which gives me very little room to juggle with dates.
If I decide not to fly HKG-SIN-BOM, can I still use the BOM-LHR leg of ticket to salvage something out of it? Or do I have to get it reissued with HKG-SIN-BOM as surface to use the last leg?