How do you make a realistic fictional world?

No, the exact dates are not at all necessary, unless there's an event you want to bring up.

Yes, however, if you make it using cheap plastic, it will look fake.

You can experiment with different shades of the colors you would like to use on a separate scrap of paper. Try sketching out a single peak/curve and just shading that....

Make sure to draw detailed curves and remove the guide lines to make your fire look more realistic. You should also make sure to color it to add more realism.

A realistic zombie is 3D, as zombies are dead people, and people exist in 3D.

Using lots of detail and shading to make it look realistic. Draw what you see, or imagine.

Start with light strokes of pencil and keep adding detail as you go. If you take your time with it you can add more and more detail. Try looking at...

Try looking at some reference pictures and add detail. For the big foot monster try giving it a scarier face. The eye monster you can add more detail and put...

Think about where the light source is and look at reference pictures. Maybe even try recreating the scene in real life!

If you're not married then you should, since it increases your relationship. Otherwise, it's not really necessary. But you can if you like.