probelmas del estudio

i don't know correctly use the prep. in spanish.
For example, ella se ocupa (en) de limpiar la casa (e) y fue de una sala a otra. DE...A...
Ella llamaba de casa en casa pidiendo amparo. DE...EN...
otros: de vez en cuando .de cuando en cuando . de tiempo en tiempo
who can tell me differences? muchas gracias de fernando

Sorry if i do any mistake, the English is not my language...

Well, when you say "De una sala a otra", this means that she goes first to one room and then she goes to another room, cleaning them in order.

In the second example that you write, when you say "Ella llamaba de casa en casa", this means that she goes to a lot of houses trying to get help.

The differences between the two expressions is that the first one we use it when something is do it in order. And the second one no needs order.

To be honest I understand that this two expressions are difficult for you, because they means practically the same and it's hard to use them in the correct situation.

I hope you understand me!