You have an object just named “Cube” that is hidden in viewports, but not in renders:
This object obscures the camera:
Either delete the object or disable it for renders as well, and your problem will be resolved.
Easy - Since the other "color" in your image is black, all you have to do is connect it to the Emission input of the Principled BSDF. You'll probably want to increase the strength a bit as well (underneath). Don't forget to turn on Bloom in the Render Properties tab to make it glow properly:
It's hard to say for sure without seeing the file.
But I believe you're probably seeing places where the reflections shoot off into infinity.
Let's think about glass, which is one place where you mentioned problems. A ray either goes through the glass or reflects from the glass. You can get vastly differing depths depending on which it does. The depth ...
To echo @brockmann (who commented), eight samples is very, very, very low. If your graphics card is working with cycles render, I would at least use 512 samples and work from there.
Edit: I was unable to find questions on what samples are, so I guess I’ll explain it myself. A “sample” is one shot of data for rendering, and more shots mean better looking ...
You use Emitter particles for your static particle crystals ("sprinkles"). For static particles that don't change their position like grass, trees, sprinkles, sesame seeds on a burger, ... it's better to use Hair particles. They are static and always dead.
Emitter particles are used for animation mainly. For birds, fishes, moths, dust, and fluid. ...
change spot strength to 1000
change glass material to :
and most important change these: (blend mode and shadow mode)
and you will get :
to change blend mode in 2.79 checkout these answers:
Material Opacity in viewport?
How to see Cycle's material transparency in 3D View
I figured it out! For some reason you cannot have "Freestyle SVG Exporter" and "Freestyle" both enabled in the render properties. By unchecking "freestyle SVG exporter", I finally could see an outline!
It seems to be a problem with the Radeon RX cards if I understand this bug report correctly, updating the card drivers can help in some but not all cases as far as I've read:
It seems as though, as of Blender 2.92, baking a tangent space normal map without using Selected to Active does not work correctly in the presence of modifiers. I have opened issue T87449 on the Blender bug tracker about this.
In the meantime, there are a few workarounds:
Apply modifiers before baking. This is probably the best workaround, since it’s easy ...
Open the Viewport Overlays popover in the upper right of 3d viewport, to the left of the Viewport Shading Mode buttons, the downward arrow next to the two overlapping circles.
Check Statistics. If it doesn't appear, try going to a different display mode (Wireframe or Solid) then back to Rendered Mode.
You should then see render progress, as well as the ...