Can one flight stop on the way and sell every leg?

Yes — a chained flight. Research a destination, type the stops under Or choose your own stops (for example Bengaluru to Mumbai with DEL), and keep Sell tickets on every leg ticked. The aeroplane flies BLR → DEL → BOM and back under one flight number, and sells three markets: BLR–DEL, DEL–BOM and BLR–BOM.

• Seats are shared leg by leg. A seat sold Bengaluru–Delhi is free again from Delhi to Mumbai, so a chained flight can sell more tickets than it has seats.
• One set of fares. Each market is priced at the same fraction of its own recommended fare as the route is of its own.
• No double counting. If you also fly Bengaluru–Delhi nonstop, that market is split between the two routes.
• Up to three stops. A stop only has to be on your map — it does not need to be a hub.

Untick it and the stop is a technical one: fuel and nothing else, which is how every route with a stop worked before. You can switch an open route either way from its card.