K&F Concept 55mm variable ND filter you are asking, you mentioned your Minolta 24-70mm vintage lens is 55mm, just please go ahead to purchase, please do not worry about it. as long as the lens size and the filter size is the same, then works. hope this helps. 

You need a Minolta AF to Sony E/NEX adapter. The MD/MC Minolta mount is different from the AF mount, so the AF lenses don't physically fit the MD-NEX adapter. 

You need a Minolta AF to Sony E/NEX adapter. The MD/MC Minolta mount is different from the AF mount, so the AF lenses don't physically fit the MD-NEX adapter. 

Could you please update us your full Minolta lens model ?as Minolta has MD MC and AF mount, K&F Concept MD-M4/3 is suitable for: Lens: Minolta MD MC Mount lens(not for Minolta AF mount: KF06.157) Camera: Micro 4/3 (MFT) mount mirrorless camera like Olympus PEN, OM-D series, Panasonic Lumix DMC-G1, G2, G3, G10, GX1, GH1, GH2, GF1, GF2, GF3, GF5, GH4, Panasonic AG-AF100 Mirrorless Digital Cameras, Black Magic Pocket Cinema Camera (BMPCC) 

MD-FX you are asking, the button you asked is a lens release button, when you want to take the lens off, you need to press this button down, hope it helps and please trust to purchase.