Can a person that is not authorised as an investment firm but meets the requirements of Article 53(3) of MiFID II be a member or participant of a regulated market or an MTF?

Article 18(3) of MiFID II requires that investment firms and market operators operating an MTF or OTF establish, publish and maintain and implement transparent and non-discriminatory rules, based on objective criteria, governing access to its facility. A similar requirement is applied to regulated markets through Article 53(1) of MiFID II. What sort of behaviour or restrictions should be considered as non-objective, or discriminatory?

Are actionable indications of interest subject to the order record keeping requirements for Investment Firms and trading venues under Article 25(1) and (2) of MiFIR?

How shall Field 30 (Quantity) in Commission Delegated Regulation (EU) 2017/590 Annex I Table 2 be reported for a transaction where there have previously been acquisitions or disposals that are excluded from the meaning of a transaction? For example, a decrease in notional amount in a financial instrument which has previously had pre-determined contractual down payments exempted from transaction reporting under Commission Delegated Regulation (EU) 2017/590 Article 2(5)(j)?

Could there be circumstances where the buyer and seller in a transaction report made under Article 26 of MiFIR are the same?