How to handle dynamic drop down list?, e.g while creating users it need to pick country from a drop down list

Ans:
Insert below line before the request having countries details

web_reg_save_param_ex( "Parameter=country" "LB=\>", "RB=</option>", "Ordinal=ALL", SEARCH_FILTERS, LAST);

It will store all the country details in CountryName array, we can access it starting from CountryName_1

Count of elements can be counted with CountryName_Count

It is a lr variable so we can access it using lr_eval_string function

lr_output_messge(lr_eval_string(“{CountryName_1 }”));