Is it possible to loop though specific data attached to the participants?

Suppose I import the participants' email addresses along with 2 additional features, say "sex" and "age".

Then I want these two data fields, "sex" and "age" to get looped through the survey to appear in the participants' answers.

Is that possible with LimeSurvey?

yes...it's pretty easy; just prefil an equation type question with one of the following "keyword":

{TOKEN:FIRSTNAME} inserts the value from the "firstname" field in the tokens table
{TOKEN:LASTNAME} inserts the value from the "lastname" field in the tokens table
{TOKEN:EMAIL} inserts the value from the "email" field in the tokens table

{TOKEN:ATTRIBUTE_1} inserts the value from the "attribute_1" field in the tokens table
{TOKEN:ATTRIBUTE_2} inserts the value from the "attribute_2" field in the tokens table
etc...

manual.limesurvey.org/Adding_a_question#...on_from_tokens_table