2. Please explain the results of the 'shadow length over 24 hours' experiment.
What experiment? I haven't seen any details of any experiment.
I think that my source - I saw it in a documentary on The BBC a few years ago - is as good as the source you always give for your experiments - Rowbotham wrote about it in the 1880s.
I could ask one of the scientists at the Scott-Amundsen South Pole base to repeat it, if you like.
It is well-documented that Amundsen took sextant readings of The Sun (to determine his lattitude) for a full 24 hours whilst at The South Geographical Pole:
http://www.southpolestation.com/trivia/igy1/polesurvey1.html
So The Sun was clearly visible in the sky for a full day - clearly impossible if it were in "orbit" around The North Pole on a Flat Earth.
The declination of The Sun would also have been constant at The Pole, within the experimental error of his Edwardian instruments.
At last - Amundsen's own words!
"soon after 11 p.m. -- we were out again, and ready to catch the sun; the weather
was of the best, and the opportunity excellent. We four navigators
all had a share in it, as usual, and stood watching the course of the
sun. This was a labour of patience, as the difference of altitude
was now very slight. The result at which we finally arrived was of
great interest, as it clearly shows how unreliable and valueless a
single observation like this is in these regions. At 12.30 a.m. we
put our instruments away, well satisfied with our work, and quite
convinced that it was the midnight altitude that we had observed. The
calculations which were carried out immediately afterwards gave us 89 [degrees]
56 [minutes] S. We were all well pleased with this result."
http://www.fullbooks.com/The-South-Pole-Volume-22.html