As the sibling comment has mentioned Unicode in DNS uses a punycode encoding but even further then that the standard specifies that the Unicode data must be normalized to NFC[0] before being converted to punycode. This means that your second example (decomposed e with combining acute accent vs the composed variant) is not a valid concern. The Cyrillic one is however.

[0] https://www.rfc-editor.org/rfc/rfc5891 § 4.1 "By the time a string enters the IDNA registration process as described in this specification, it MUST be in Unicode and in Normalization Form C"