would it fit a seiko SSB325?

It will fit any watch that requires a 20mm band.

Which style is it? There are 2 different styles shown in the pictures.

The two photos show both sides of the same band. I have the side with the rectangles facing my wrist. It is a nicer band than the one that came on my watch. If you need a band this one is great.

Does this band fit the seiko skx779 (original black monster)?

It will fit any watch that requires a 20mm band.

Does this fit 7S35-00F0?

Not sure. I measured (or the jeweler did), the bar that it connects to on the watch. The jeweler did not have (or could order) one that matched the original band. I found these on Amazon and be length(width) of the connection bar was the same as that of the watch and the original band. I took the new one to the jeweler and had them put it on. THe bank looks exactly like the original as design but is just a tad longer than original band. The "mm" width is the important thing. BTW, my husband was thrilled bc it is his favorite watch.