To hide page numbering:

The page numbering is in a header or footer, so you need to edit the header or footer to fix this.

To restart page numbering.

Page numbering can be controlled by section breaks. You need to insert at least one section break to make this happen. Each time you insert a section break, the numbering can restart.

Changing styles of page numbers between i,ii,iii to 1,2,3.

Select page numbers in the footer section. Just remove the link to previous. This way the formatting will not be linked to the previous header or footer and you'll get good page numbers starting in a different styles, especially useful starting afresh.