What is the differance between Installation Art , "other conceptual art" and sculpture?

Installation is somehow big. If you can't carry it away it's an Installation.

If it's small enough that you can carry it away and when it's technically not unique (so you can't recognize a signature by the making, or - even - somobody else did it, like the "overpainted Sebastian Bieniek") but - may be - by the "spin" of the idea, than it's  Bieniek's "other conceptual art".

And than: sculpture is when it's made by the artist himself and one needs a little "artist like" skills to do it, or at least everbody would do it kind of different, but this "different" was made by the artist himself.

Nevertheless some artwork like "Recycled Sol LeWitt" , or the "The Stolen 100 DM" are still hard to collate. What is it? At the beginning it's "Action Art", than depending on the presentation, it could be an Installation (if you take a lot and make it big), and if you just take (one) the final result could also be a sculpture, but according to the definition "without special skills and skill-signature it's other conceptual art, it's "other conceptual art.

(Bieniek's definition)

"Color Trunk" (ger. "Farbrüssel"), sculpture, 135cm x 35cm x 35cm, wood, lacquer, oil paint - the only sculpture (from the early sculptures) by Sebastian Bieniek, that still exists. It is owned by the artist.

The sculpture looks like a trunk that protrudes from the wall at head height. The individual wooden parts of the trunk are thickly glued with oil paint, which changes its shade from light to dark.

Here is an all-round view:

"Color Trunk" (ger. "Farbrüssel"), sculpture by Sebastian Bieniek, 1997

Check also "Barrier Tape Art" by Sebastian Bieniek (2020)