What is the ruling on participating in a free online lottery that requires answering three questions, without paying money?

If the company issues lottery tickets for a fee, and you obtained them for free, this indicates that the company is involved in prohibited gambling. Lottery tickets are a form of maysir (gambling), which is forbidden by textual evidence and scholarly consensus, based on the words of Allah the Almighty: (O you who have believed, indeed, intoxicants, gambling [maysir], idols [ansāb], and divining arrows [azlām] are but defilement from the work of Satan, so avoid it that you may succeed. Satan only wants to cause animosity and hatred between you through intoxicants and gambling and avert you from the remembrance of Allah and from prayer. So will you not desist?) Al-Ma'idah/ 90-91.

Therefore, you must dispose of this ticket, and it is not permissible to participate in the competition or expect anything from it.