Can I create a mono-deck (example: mono- with just life cards and a mark) or do I have to use cards from all the spiritual elements?
Yes, you may. You're not required to use cards from each of the four elements in a group.
Do all the decks we make in the tourney have to align with one group, or can we use decks from each group?
You are not limited to using decks from just one group.
we can use only two cards mark from the grou or we have to use all four?
You can use any number of elements in a single group. For example, a Material deck can use cards and a mark from any of the following elements:
.