This hack gives you infinite continues. Nothing else was changed. If you're tired of replaying the first few levels and the Konami code makes it way too easy, this should be a good middle ground.
Database match: Contra (USA)
Database: No-Intro: Nintendo Entertainment System (v. 20210216-231042)
File SHA-1: 4B9FAD65727042595C5820CA03BC32BFD72DE5E7
File CRC32: 52CD5CD8
ROM SHA-1: 979494E7869AC7AB4815FDBD1DC99F893F713FBF
ROM CRC32: F6035030