If you want to check the current availability yourself, use these specific search queries on the Internet Archive (archive.org):
A: Yes. The "UPD" includes the theatrical cut as a bonus feature, encoded at 720p. It does NOT include Kamen Rider vs. Ambassador Hell (you need to search for that separately). kamen rider 1971 internet archive upd
Since the Archive is no longer a reliable primary host for the full series, use these community-verified alternatives: If you want to check the current availability
Many users upload full episodes of the 1971 series, often with English fan subtitles. These are frequently updated in "TV Series" or "Tokusatsu" collections. Ambassador Hell (you need to search for that separately)
Kamen Rider Volume 1 À 3 : Free Download, Borrow, and Streaming : Internet Archive. Internet Archive Full text of "TICOM Archive"
: The category for all series produced between 1971 and 1989.
While you might find episodes on the Internet Archive, they are often taken down. For a stable viewing experience, checking Shout! Factory TV or Tubi is the best legal update for the series.