The hack is for the japanese version of the game.
Contra is a Konami game which features a loop mechanic. Every time you beat the game it starts over slightly more difficult. This hack modifies the game such that the game is always at its hardest possible difficulty. This seems to happen at about the 7th loop. So, this is the official hardest mode by Konami.
Already included in the patch is the camera fix for 2 players mode.
The hack is compatible with the translation http://www.romhacking.net/translations/1451/
Database match: Contra (Japan)
Database: No-Intro: Nintendo Entertainment System (v. 20180803-121122)
File SHA-1: 376836361F404C815D404E1D5903D5D11F4EFF0E
File CRC32: 8A96A3C4
ROM SHA-1: BE9DD65BE8DB897978DD34533DD3A037784A8EE9
ROM CRC32: B27B8CF4