What is the ruling on my work in a marketing research company that requires me to interview beneficiaries, but I provide answers myself for questions I deem unhelpful? Is the money earned from this work unlawful (haram), lawful (halal), or mixed, and how can I purify it if it is mixed? What is the ruling on performing Hajj with it?

What the questioner did by answering on his own initiative and not presenting the questions he was assigned is not permissible. A private employee must abide by the agreed-upon conditions, unless they contradict Islamic law. If he falls short, the employer has the right to deduct from his salary commensurate with his negligence. He must seek absolution from the company and ask for their forgiveness, or return a portion of the payment proportionate to his shortcoming. Otherwise, his liability remains outstanding and his wealth is mixed (with unlawful earnings). His Hajj is valid, despite the sin of acquiring unlawful money.