How to bring up a precise Emoji in the iOS QuickType menu

Solution 1:

To answer both of your questions:

1. No, you cannot type all emoji using QuickType. It's currently not possible to quicktype 😈.
2. See below.

Examples that can be typed:
🤩 star struck
🇯🇵 Japan
🎮 video game controller

Examples that do not adhere to Unicode descriptions:
🖲 controller ("trackball" does not work)

You can test most matches on macOS using the Emoji & Symbols popup: cmd+control+Space

Examples that can be typed on macOS (10.13.3), but not iOS (11.2.6):
🏇 jockey ("jockey on racing horse")
🤪 zany ("zany face")

On macOS the localised keyword data is inside /System/Library/PrivateFrameworks/CoreEmoji.framework spread across 4 strings files:

1. AppleName.strings (descriptive name) [1549 entries in English]
2. CharacterPicker.strings (for searching) [1505 entries]
3. FindReplace.strings (for suggestions/predictive) [1060 entries]
4. Voiceover.strings (for macOS speech) [1764 entries]

Quickly comparing FindReplace.strings with AppleName.strings or any other complete list of Emoji shows that some are missing.

Also, iOS seems to be lagging with regards to its copy of this data.