1) There is no single hardest language to learn as it depends on an individual's first language and other factors. For English speakers, Hungarian has proven very difficult due to its complex system of 35 grammatical cases, though Tabassaran has even more cases.
2) The degree of difference between one's first and second languages affects difficulty, with more similar languages like Portuguese being easier for Spanish speakers to learn than dissimilar ones like Chinese.
3) While Chinese's writing system presents challenges, its difficulty depends on one's first language, as Japanese speakers already use Chinese characters and may find learning Chinese writing easier than a new script. Overall, no single language can be defined as the most difficult for all learners