Can I treat pooled cross-section as panel data and do regression analysis? I work with a large survey data that is pooled cross-section, i.e, people interviewed are randomly chosen in each time period. This is not panel data. But, I aggregate the individual cells according to age and gender groups and then run the regressions. Now that I work with age-gender groups, is this considered panel data?
Yes, you can consider this as panel data, but the key is to understanding why, as this affects how you explain and interpret your panel regression. In treating each cohort as the same unit over time, you are assuming that each cohort has a constant, unobserved fixed effect. That is, people in a particular age category and gender tend to have an unobserved effect on the dependent variable that is different to other cohorts.

Please note:

Age increases over time, so, for example, the group aged 30–34 in year 1995 should be treated as the same group as the 35–39 year-olds in 2000. I suggest your time variable increases in steps of five years, as you indicated that your age categories are five-year bins.