If you want to go the canon way then go dirt cheap on the body as the newer models don't have a significantly better image quality, get a used 600d, eos M or something like this. Download and instal magic lantern on it and use the vision color picture style. Then with the money left get good lenses with fast aperture, a tripod with fluid head and a good shotgun mic with +20db feature like the takstar or the rode videomic pro if you can afford it.
I shot this with a 600d and an eos M and it looks totally fine to me. https://www.youtube.com/watch?v=QB8RsA-AAo4
That said if you can afford it I advise you to get something better strait than a canon dslr, the panasonic G7 is great, the sony a6300 too, both are very cheap for what they offer.
What you feel is right.
I always have a bottle of water, a multitool and some food. Usually I like to have a small umbrella.
It depends on the laws of the country you are in, but seing the situation I think you are totally fine.
1.What are the main differences you see when comparing modern day cinematography and classic cinematography?
It's hard to point one or two differnces as there are so much example in both classic and modern cinematography that you can find everything, most of the cinematography grammar was already found in the 1920. But if I had to find one I would say lighting.
2.Do you prefer traditional filming cameras or digital cameras to produce your projects?
Digital, it's easier, safer, cheaper, and better in every aspect, that's why film camera are less and less used, it just doens't make much sense to use them today. I've shot film on film, it was a fun and nice experience and I am happy to have done it but today I would go digital only.
3.Do you think that today's technology has improved the look of the final product of films?
Yes, it has a lot, now camera are sensitive enough to film with the moonlight as the only source of light. The revenant has been shot only with natural lighting and it looks amazing. Dynamic range, frame rates, size, gear price, it has allow for new way of filming.
4.What is the most difficult process in producing a film?
Getting someone to pay for it. Honestly pre-production is very hard, you can spend years trying to sell your project it is really the hardest part, at least until you are a well known and much wanted director but until then that's clearly the hardest part.
5.About how long does it take to produce a short film?
It depends on what you are doing, from a few minutes to years.
The answer is no, 4k makes lenses issue more visible so a cheap lense will look worst in 4k. BUT Sony lenses looks great on the a6300 because there is in body lens compensation, the images are transformed inside, aberrations are removed, distortion is compensated and in the end it looks like the lense is optically perfect. If you want you can disable it in the menu and your lenses will look bad again :-)
It's a great feature it means you can get great image quality from cheaper made lenses. I also have the a6300 and the 18-105 and this combo works very, very well, I leave my canon lenses at home more and more.