What can I do with red chests, doors and crystals?

Solution 1:

So these "devil" (red and spiky) props are "guardian" (purple crystal) props that received damages.
While interacting with guardian props requires to spend crystals and fills up the guardian gauge (down right corner of the screen), interacting with devil props costs life (can be hearts or shields) and fills up the devil gauge.

A full guardian gauge gives access to the guardian room (via teleporter) where you can choose between two items for free.

A full devil gauge opens the devil room where sacrificing a heart slot allows you to choose between three items.

Solution 2:

According to discussion on Reddit, you can walk into the red spiked chests, sacrificing health to make them openable once more.