Are ulative frequency polygons and curves only used for grouped data?

A ulative frequency polygon can be used with ungrouped data. A cf polygon for ungrouped data is sometimes called a "step polygon". I believe that cf polygons are normally used with grouped data because then you can use the diagram to estimate the proportion of the data less than or greater than a particular value and the quartile and median values. If the data are ungrouped (raw data) you can use the data directly to determine those values and so you do not actually need to use a cf polygon.