For the most part, no. Crystal growth is not dependent on the amount of light it gets. They’re more dependent on things like temperature and the amount of liquid available. They can have an effect, though, in very specific crystal situations. For example, crystals of silver bromide and silver iodide break down into silver metal when they’re exposed to light. Most crystals though form both at the surface and deep within the earth. A lot of them form in the area around volcanoes!

I am not quite sure what aspect you are asking on the effect of the light upon the crystal growth, as it is unclear to me the way of crystal growth you are talking about and how the light is shed during the crystal growth. There are many ways to grow the crystals with or without light. As a matter fact, there is a good way to get large single crystals using the focused light in the optical mirror furnace. This is a widely used way to obtain the large single crystals in the physics community, not involving too much chemistry. In such way, the focused light plays the key role.

To me, depending on the process of crystal growth and how the light is used, it will or will not play a role in the crystal growth. Certainly, if the light is applied effectively, it will promote the crystal growth.

Depends on the crystal. Light tends to break chemical bonds. If those chemical bonds are holding back atoms that would otherwise be part of the crystal, then the light will free them and let the crystal grow. If the light breaks up the bonds holding the crystal together, then the crystal will dissolve. Different colors of light break different kinds of chemical bonds, so it depends on what the material is made of.

For most cases you will come across, light will not affect how much the crystal grows. This is because the forces responsible for the position of atoms are very strong, whereas the effect of visible light tends to be much weaker. This is not always the case. For example, you know that some materials decompose when exposed to light, so you can imagine quite easily that in this case this would interfere with the growth of the crystal. Additionally, you also know that light can heat things, so you can imagine some extreme situations where you have such intense light that you melt the materials.

However, this can be a good thing, and this is actually how we grow really large crystals for ceramics and other materials that melt at really hot temperatures. We can take a big rod of powder that's been squeezed together, and heat it up using several really bright lightbulbs and mirrors to direct all the light to a small area, which then melts the powder and causes it to crystallize.