It's possible to use create an MCP installation for versions of Minecraft where there hasn't been a full MCP release. It takes a little bit of manual setup, but the end result is highly useful.
conffolder, and change
ServerVersionto the version you want (for instance, 1.12.2).
Download the SRG zip for the version you want; these can generally be found at
http://mcpbot.bspk.rs/mcp/<version>/mcp-<version>-srg.zip(for example, http://mcpbot.bspk.rs/mcp/1.11.2/mcp-1.11.2-srg.zip) or at
http://files.minecraftforge.net/maven/de/oceanlabs/mcp/mcp/<version>/mcp-<version>-srg.zip(for example, http://files.minecraftforge.net/maven/de/oceanlabs/mcp/mcp/1.12.2/mcp-1.12.2-srg.zip). (For 1.12.1 and 1.12.2, only the minecraftforge link works)
Extract that zip into the MCP