The Earth's orbit is an ellipse, not a circle, and therefore the Earth speeds up or slows down depending on where on its orbit it is at the time. In turn this means that the duration of the solar day fluctuates from day to day, from a bit under 24h to a bit over 24h and back.
So if you take a picture every 24h precisely the sun will appear to move horizontally a little bit on top of the expected vertical movement.
It... depends. There is some great tooling for Python -- this was less true only a few years ago, mind you -- but the landscape is very much in flux, and usage of the modern stuff is not yet widespread. And a lot of the legacy stuff has a whole host of pitfalls.
Things are broadly progressing in the right direction, and I'd say I'm cautiously optimistic, although if you have to deal with anything related to conda then for the time being: good luck, and sorry.