Opening name change of one game at Chess.com

Question

Here are the first few moves of a game that I played at chess.com and the name of the openings is shown by the system:

1. c4 (English Opening) c5 (English Opening; Symmetrical Variation)
2. Nc3 Nc6 (English Opening; Symmetrical, Two Knights Variation)
3. g3 (English Opening; Symmetrical, Two Knights, Fianchetto Variation) Nf6
4. Bg2 (English Opening; Angelo-Indian Defense) g6 (English Opening; Symmetrical, Two Knights, Fianchetto Variation)
5. e4 Bg7 (English Opening; Fianchetto, Ultra-Symmetrical, Botinivik System)
6. d3 (English Opening; Fianchetto, Ultra-Symmetrical Line) O-O (English Opening, Angelo-Indian, Queen's Knight Variation)
7. Nge2 (Sicilian Defence, Staunton-Cochrane System) d6
8. O-O (English Opening; Fianchetto, Ultra-Symmetrical, Botinivik System)

Why did the name of the opening of this game change back and forth so many times in the first few moves? I am particularly amazed that we entered Sicilian Defence at move 7 and came back to English at move 8.

Answer 1

Before a sufficient number of moves is played, the exact name of the opening cannot be determined. And the key term to answer your question is transpositions:

... is a sequence of moves that results in a position that may also be reached by another, more common sequence of moves. Transpositions are particularly common in the opening, where a given position may be reached by different sequences of moves (Wiki on chess transpositions).

So, c4 at move 1 is commonly referred as the English opening family; however, certain Sicilian (and other ones!) defense positions can be reached from it (soundly or unsoundly — is a different question). Moreover, in many cases there is no established convention on how to call a position (especially when amateur players play the opening); hence, some choice is made by a website interface, and it might be that another website can make a different choice for the same position.