Re: '20 of which must be made on mobile'
The current version of Bing Rewards (sometimes) distinguishes between PC and mobile searches; currently users can earn 15 credits on the PC and 10 on mobile (regardless of device or OS used). That said it would be nice if Microsoft gave extra credits to those of us who do use W10 Mobile.
Thank you, Cortana!
Please tell me more about Windows 10 mobile.