new with impress.js

Hi everyone:

I´m trying to make a presentation with impress.js in I am wondering about some issues, first at all:

Does impress.jss have an "step back" function or metod? I´m triying to use an index, and i need tome come back to that slide every moment, but i don´t see how to

Does impress have any function of opassity, I wuold really like to hide elementes in the same slide while I am doing a step. For example first I present a phrase that says hellos, then I make an step with my arrow, it`s hide and appear another phrase down the first one thats says world.

An finally I am trying to make that the transition "go inside" of my slide (like in the example were its says "visualize your big thaughts" and them its says, "and tiny idea" but its doesn´t work with the slide.

Regarths everyone!