PlusPoints are valid on all UA fares, along with certain Lufthansa (LH) and ANA (NH) fares. PlusPoints are not valid on Singapore Airlines (SQ), although if the SQ flight is just SIN-DPS, I doubt you'll care very much. It's the operating carrier that matters, so if your Germany to Singapore flight is operated by LH and you have a qualifying fare, you can list PlusPoints -- 40 per person per leg you want to upgrade.