Does the ICAO definition of an "aircraft" include a minimum altitude capability?

Question

The German air law includes in their legal definition of a "Luftfahrzeug", which is the equivalent of an aircraft, other devices intended to operate in the airspace if they are capable of being operated more than 30 meters (100 ft) above ground or sea level.

Does an equivalent to this 100 ft threshold exist in ICAO documents or other international regulations? If yes, where?

The background of my question is: if an unmanned aircraft has a technical feature preventing it from flying above 100 ft, would it still qualify as an aircraft and would all regulations about aircraft apply?

I would also like to know, why the 100 ft threshold was put into the German (or other) laws. I could image that it was intended to exclude wing in ground effect crafts from the aircraft category. Is a wing in ground effect craft an aircraft according to ICAO definition?

Answer 1

Is there a lower altitude threshold in the ICAO definition of an aircraft?

No.

Is a wing in ground effect craft an aircraft according to ICAO definition?

No.

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I believe the ICAO is based on the Chicago Convention

The 2006 9th edition begins

THEREFORE, the undersigned governments having agreed on certain principles and arrangements in order that international civil aviation may be developed in a safe and orderly manner and that international air transport services may be established on the basis of equality of opportunity and operated soundly and economically

Although this has a section on definitions, it doesn't define aircraft.

The ICAO ADREP taxonomy contains this definition:

Aircraft. Any machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the earth's surface. (Annex 8)

That appears to exclude vehicles whose support relies on ground effect only.

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Why [was] the 100 ft threshold [...] put into the German (or other) laws?

That might be better answered in law.se