How many variations has Réti made?

1.Nf3 is not the Reti Opening.  Another one of chess.com's idiotic mis-namings of openings.

1.Nf3 has no name yet.  King's Knight opening, if you have to name it.

By definition, the Reti Opening is 1.Nf3 d5 2.c4.  The following, for example, are not Retis:

1.Nf3 c5 2.c4 - English Opening

1.Nf3 Nf6 2.c4 - An English for the moment, but can transpose to a Reti after say, 2...e6 3.g3 d5

1.Nf3 d5 2.g3 - This could transpose if a later c4, but this is not a Reti.

Also, the Reti Gambit is not 1.Nf3 d5 2.c4.  There is no "Reti Gambit Declined".  It is only considered the Reti Gambit if Black takes with no effort by White to immediately get it back, like 1.Nf3 d5 2.c4 dxc4 3.g3 or 1.Nf3 Nf6 2.c4 e6 3.g3 d5 4.Bg2 dxc4 5.O-O.

Also, the Reti Gambit is a line against the French with 2.b3.

What about Reti opening, the potato variation?

Did Réti create that?