I have a 2015 MacBook Pro which is going to be the oldest-supported model for macOS 12 Monterey, so Apple seems to be supporting computers for ~7 years.
Many of the most common Chinese characters used in Mandarin aren’t really used in Japanese, so especially for the most common words there isn’t that much overlap.
Yeah, exactly. I passed N1 which requires ~2000 kanji, but I still frequently encounter words with kanji I haven’t encountered/don’t know the readings of.