Base on this scenario and for question one please provide references to the case law- use different cases

Kitchen Ltd is a medium-size kitchen items manufacturer. Kitchen Ltd is currently the defendant against a group of retailers who have claimed that it has supplied them with a quantity of microwave ovens that have all overheated and exploded in use, causing injury to persons. The action is currently being contended by Kitchen Ltd, in the Court of Appeal. A question of interpretation of the (fictitious) Oven Safety (no 2) 2019 directive has arisen before the Court of Appeal and the court is minded referring the matter to the Court of Justice of the European Union (CJEU).

Based on this scenario

1. What are the characteristics of a 'court or tribunal' within the meaning of Article 267 TFEU? Please provide references to the case-law.
2. Discuss obligation and discretion to refer to the CJEU.
3. In the present scenario, under what circumstances would the Court of Appeal have no discretion to refer to the CJEU?
4. Discuss instances when an obligation to refer under paragraph 3 of Article 267 TFEU is waived.
5. How does the doctrine of acte clair operate to mitigate the obligation to refer a question to the CJEU concerning the interpretation of union law?