Context: All graphic, format, and private use characters have a unique and immutable name by which they may be identified. This immutability has been guaranteed since Unicode version 2.0 by the Name Stability policy. In cases where the name is seriously defective and misleading, or has a serious typographical error, a formal alias may be defined, and applications are encouraged to use the formal alias in place of the official character name. For example, U+A015 ꀕ YI SYLLABLE WU has the formal alias yi syllable iteration mark, and U+FE18 ︘ PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRAKCET (sic) has the formal alias presentation form for vertical right white lenticular bracket.

Question: What policy guaranteed that characters have a unique and immutable name?
Answer: Name Stability policy

Question: What happens when a name is defective or misleading?
Answer: a formal alias may be defined

Question: How long has this name immutability been guaranteed? 
Answer: since Unicode version 2.0

Question: What policy identified misleading characters?
Answer: Unanswerable

Question: When an error is found, what is used in place of a formal alias?
Answer: Unanswerable

Question: When was the formal alias yi created?
Answer: Unanswerable

Question: What is an example of a symbol that does not use a formal alias?
Answer: Unanswerable

Question: Which types of characters do not have unique names?
Answer: Unanswerable