The "1.12.2" version refers to the World of Color update—a highly popular era of Minecraft known for its stability and rich features. It includes everything you love: glazed terracotta, parrots, concrete, and a vast array of mechanics that define the classic Minecraft feel.
Would you like step-by-step instructions for hosting your own private Eaglercraft 1.8.8 server instead? That is generally more fun for multiplayer.
: For the best "unblocked" experience, download the standalone HTML file from a repository to run the game locally without needing an active internet connection to load the assets.
Gameplay
This ensures you have a personal copy that won't be taken down.
Eaglercraft shines in its multiplayer capabilities.
For Eaglercraft 1.2.1 unblocked, start in singleplayer to ensure the client works. Then, find a public server list (search "Eaglercraft server 1.2.1").