What is the interaction between mold earth and create bonfire?

If I cast create bonfire in a 5 foot unoccupied space. Then next round cast mold earth to excavate that same area creating a 5 foot pit underneath the fire; Does the bonfire fall or stay at ground level?

This came up in game. The bonfire is magically created and does not need to burn fuel. So it could float. But does it? Is there a precident?

Can Create Bonfire be placed in a way that affects multiple squares?

The Create Bonfire cantrip creates a bonfire which “fills a 5 foot cube”. It deals comparable damage to other cantrips, making one assume it’s meant to only deal it (reliably) to a single target. But, if playing on a grid, is there something actually preventing a character from making the 5 foot cube be placed at an intersection, possibly damaging four creatures?

How much illumination does Create Bonfire provide?

Create Bonfire (XGtE p152):

You create a bonfire on ground that you can see within range. Until the spell ends, the bonfire fills a 5-foot cube. Any creature in the bonfire’s space when you cast the spell must succeed on a Dexterity saving throw or take 1d8 fire damage. A creature must also make the saving throw when it enters the bonfire’s space for the first time on a turn or ends its turn there.

I am aware that spells only do what they say they do, but usual bonfires do create light. While illumination is not mentioned, it is hard to imagine a bonfire without flames and light, and the spell does not indicate in any way that this is not a usual bonfire.

It should be brighter than a torch for sure, but how much exactly?

Is a creature that stands in a bonfire from Create Bonfire affected twice in one turn?

If a caster casts the Create Bonfire cantrip and creates a bonfire in the square a creature is occupying, and the creature either chooses to stay in a square occupied by the bonfire or is forced to stay in that square, is the creature damaged twice? Once when the fire is created and once when the creature ends its turn there?

Create Bonfire says:

Any creature in the bonfire’s space when you cast the spell must succeed on a Dexterity saving throw or take 1d8 fire damage. A creature must also make the saving throw when it enters the bonfire’s space for the first time on a turn or ends its turn there.

If so, then this cantrip looks like it would be more powerful than other damage cantrips, particularly if the caster’s companions have some way to restrict movement. Is that correct?