Yes I have done last year in one day haridwar rishikesh mossori in one day on bike bike with friends you can watch me video on YouTube please search PPL GooD
It will be too hectic but possible, but Moosourie and Haridwar are places where staying a night or two feels awesome and relaxing. Now your choice but it's technically possible.
Yes it's possible. but it will be a hectic tour. If you start your journey from Delhi, then reach Haridwar as early as possible, and book cab to visit Haridwar and Rishikesh. But in this plan you will miss "Ganga Aarti" at Haridwar. I will suggest you to stay Haridwar for 1day at least. if you stay Haridwar for 1day then next day you will go for Mussouri via Rishikesh. and you can try Bunjee Jumping/Flying Fox/River Rafting at Rishikesh. Or you can go directly to Missouri
Little difficult ! There are lots of things to do in Rishikesh and Haridhwar. You should stay at Haridhwar at night and capture most famous Ganga Aarti at Har ki podi. The atmosphere , vibes are so positive that you'll definitely enjoy it. You can go to Masoori in another trip. Travel less but enjoy the journey ..!!