2.61 (TD2 and TD4) In case the tender involves ethical issues, should the ethics self-assessment follow the HEU principles, answering all the relevant questions of the relevant guidance document (https://ec.europa.eu/info/funding-tenders/opportunities/docs/2021-2027/common/guidance/how-to-complete-your-ethics-self-assessment_en.pdf)?

Yes, it should. You can find more information also on/off award criterion D (Compliance with Ethics Requirements).