French adjective q

Factual Questions
1

It’s feu ma tante, but ma feue tante.

  1. What’s the difference in meaning, if any
  2. Why does the adjective agree with the noun in the second case but remain invariable in the first case? Are there other examples?
2

The expression means “My late [deceased recently] aunt”. No difference in meaning.
Another similar example is “défunt” (deceased (or inactive) for a long period of time).

Explanations (in French): Feu et défunt - Le bon usage