What is 4D like ? How is it different?

[βαθμιαίος]

Will I be able to change the shape of my body with my thoughts?

This one Ra addressed. That's more of a fifth-density ability, apparently:

90.5 ...The process of what you call physical evolution continues to hold sway into fourth density. Only when the ways of wisdom have begun to refine the power of what you may loosely call thought is the form of the physical complex manifestation more nearly under the direction of the consciousness.

...

90.7 ...In fifth density the manifestation of the physical complex is more and more under the control of the conscious mind complex. Therefore, the fifth-density entity may dissolve one manifestation and create another.

Also this one:

Are there dogs, cats, lions, tigers, bears?

62.29...Thus in fourth density the red, orange, and green energy nexi of your planet will be activated while the yellow is in potentiation along with the blue and the indigo.

In other words, yes, there will be lions, tigers, etc., but no third-density humans for a while.