Disclaimer: i have yet to see Reflection myself. the information provided is what i have looked up on the Wikia
it's advisable to watch the first and second movies. while they are sorta retelling of the Original Series and A's there are some design and story elements changed. while to my understanding the first movie is much the same in the second movie
Lindy uses Durandal instead of Chrono and the Book of Darkness's Defense Program is revealed to be called NachtWal having it's own will and new forms not shown in A's, this changes the battle between it and the Mages (Nanoha and Fate) from A's up until Hayate reprograms the Book of Darkness renaming it Reinforce where afterwards it mainly follows what happens in A's
this separates the movies from the original 2 series (primary continuity) in their own continuity (movie continuity)
it is part of the movie continuity, continuing with the history and designs in The MOVIE 2nd A's. However, as the primary continuity has zero coverage about what has happened between the early spring and winter of 0067, the story of Reflection may somehow be seen as a re-telling or supplement of this blank period.
Source: Magical Girl Lyrical Nanoha Reflection (2nd Paragraph)
as such chronologically there should be no appearances of characters from StrikerS, ViVid, ViVid Strike and Force
also while the plot for Reflection takes some ques from the Nanoha PSP Games, The Battle of Aces and The Gears of Destiny, it adds original storylines and characters as such isn't a requirement to play or understand their plot.