What is the default Expand Nomadic Region: Northeastern Asia game rule in CK3?

Default: The Northeastern Asia region is unchanged. (patch 1.20.1.2)

Does changing the Expand Nomadic Region: Northeastern Asia rule disable achievements?

No: none of its 2 settings carries the flag blocks_achievements in patch 1.20.1.2.

Game rule · Historicity

Expand Nomadic Region: Northeastern Asia

Default
Nomadic#

Expand Nomadic Region: Northeastern Asia is a game rule in Crusader Kings III (Historicity) with 2 settings: Default (the default) and Nomadic#. None of its settings disables achievements. Patch 1.20.1.2, from game/common/game_rules/00_game_rules.txt.

This section as JSON: /raw/game-rules.json

Quick answers (2)

What is the default Expand Nomadic Region: Northeastern Asia game rule in CK3?: Default: The Northeastern Asia region is unchanged. (patch 1.20.1.2)
Does changing the Expand Nomadic Region: Northeastern Asia rule disable achievements?: No: none of its 2 settings carries the flag blocks_achievements in patch 1.20.1.2.

2 settings

Default
Default
The Northeastern Asia region is unchanged.
northeast_asia_nomad_region_off
Nomadic#
The Northeastern Asia region uses Nomadic mechanics of The Great Steppe Situation. This rule will not have any effect unless you own the Khans of the Steppe Expansion.
The script checks it once, in 1 place
On actions (the game's own hooks) 1
- on_game_start_after_lobby
Every has_game_rule = northeast_asia_nomad_region_on in game/common and game/events, by the top-level object it sits in.
northeast_asia_nomad_region_on

Source: game/common/game_rules/00_game_rules.txt line 1295 (key northeast_asia_nomad_region), modifiers from game/common/modifiers, names from the English localisation; Crusader Kings III 1.20.1.2.