Yes on all four.
To clarify, the term “pair” in UTF-16 refers to two UTF-16 code units, the first in the range D800-DBFF, the second in DC00-DFFF.
A code unit is 16-bits (2 bytes), typically written as an unsigned integer in hexadecimal (0x000A). The order of the bytes (0x00 0x0A or 0x0A 0x00) is specified by the author or indicated with a BOM (0xFEFF) at the beginning of the file or stream. (The BOM is encoded with the same algorithm as the text but is not part of the text. Once the byte order is determined and the bytes are reordered to the native ordering of the system, it typically is discarded.)
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solved How does UTF16 encode characters?