Level Select
Beat the game and save it to unlock the level select.

ACTION REPLAY MAX (EUROPEAN-CODES)
(M)
BEQ6-R80J-N73PF
EHB8-2UR6-DK3N5

(INFINATE HEALTH)
UTQ7-GY3Y-NDW4Q
U0DD-DZ92-XF55Y

(INFINATE AMMO)
Y5DV-8K37-EMNEK
ME26-XKHK-N7ZHW

(MAX RELOAD)
NME1-PGBX-PVYTV
M9CB-ZPHH-YE5XA

Stealth Levels
On Levels when Stealth is required it necessarily mean that because when I was on Haitian Docks at the start I shot down the brown crate then elimanted them all using cover and the P99 silenced, the same goes with the Science Centre I elimanated them all without them even knowing I was there it was hilarious.
Feel free to tell me if this was helpful.