Can we take selenium, iodine and molybdenum all at the same time?

Yes, that's not a problem. They don't interfere with each other. Unless you're taking a supplement that has a bunch of weird ingredients and fillers in them at the same time. If you're taking the supplement brands I've recommended, you'll be fine. But if you went out and got your own and it has a bunch of strange ingredients and fillers in them, they may interfere with absorption. So that's why I like to see the exact supplements you're taking so I can review the ingredients and approve the supplement. But you're really just better off taking my recommended supplements. 

So yes, it's fine to take all 3 at the same time. Just make sure they're taken away from meals on an empty stomach, and away from other supplements.