Many plants will not root in sand as there is little mineral content for nutrition, and little to grasp onto. Some grasses may root, shallowly, but can take hold in a group that is fed water and minerals.
Sand ofcourse
No, I don't think so.
soil
Yes. Try them in both.
You put the cactus on sand. There is no seed required. Also know they cannot grow right next to each other.
Well, friend, seeds can grow in both sand and soil, but soil is generally more nutritious and provides better support for growth. Sand is good for seeds that need well-drained conditions. Remember, each seed is unique, so it's important to consider the specific needs of the plant you're growing. Just believe in the magic of nature, and your seeds will find a way to grow beautifully no matter where they're planted.
Soil, because a fertile soil nourishes the seedlings well
Depends on the seeds. If I'm sowing seeds in a greenhouse type situation, I typically use a standard potting mix (1 part each good garden soil, sand and compost) topped with about 1/4" of plain sand, sow the seed, then top with a little more sand.
Beans grow on vines, that grow from seeds.
It grows better with soil. Soil has more Nutrients. I've done some test on it Sand doesn't really grow at all with just play sand from what I've tested.
sand+life=seeds
Radish seeds grow radishes, just like apple seeds grow apple trees.