I started travelling internationally for work in 1991 - didn't know anything about FF points before then (hardly traveled).
know I joined Pan Am freq flyer right of the bat (later to be converted to Delta) => 1st Intl flight was PA JFK to Brussels in Aug '91.
The 1st hotel chain stay I can recall, is Westin Chosun in Seoul in '93.
Not 100% sure, but fairly certain 1st Hyatt was Seoul GH in ~'98