- gTLD stands for "generic TLD"[1], not a short form of global, comes from their "generic" usage. Both two categories of TLDs are in the domain namespace which is globally resolvable.
- Almost all of two-letter ASCII ccTLDs reflect the ISO country codes, from ISO 3166-1 alpha-2, but there are a few exceptions: the United Kingdom (GB) has ".uk"[2], Ascension Island (now part of SH) has ".ac", etc. (Yes, there are more non-ASCII ccTLDs: .新加坡, .УКР, etc.)
If you want to briefly take a look at how TLD registries structure their second/third level such as "k12.or.us" or "chiyoda.tokyo.jp", see "ICANN DOMAINS" section of the public suffix list[3] (note: it is not complete)
In Japan the PM's office once considered to block online piracy websites[1] with DNS in 2018. Japanese tech community fought against it[2][3][4] and it wasn't implemented.
The telco authority currently considers to block online casino websites[5] (gambling is illegal in Japan).
Actually the root is a null (empty) label rather than "."; dots are delimiters of labels, there is an empty label after "." in FQDNs. See RFC 1034 Section 3.1.