ST3SHPNLNTN3HSR1YEAR0327CarnivalMOREPEACH
Redemption Code: ST3SHPNLNTN3 - https://hsr.hoyoverse.com/gift?code=ST3SHPNLNTN3
Rewards: Stellar Jade x50, Credit x10000
Redemption Code: HSR1YEAR - https://hsr.hoyoverse.com/gift?code=HSR1YEAR
Rewards: All or Nothing x1 & Credits x5000
Redemption Code: 0327Carnival - https://hsr.hoyoverse.com/gift?code=0327Carnival
Rewards: "Sour Dreams" Soft Candy x2 & Credits x5000
Redemption Code: MOREPEACH - https://hsr.hoyoverse.com/gift?code=MOREPEACH
Rewards: Traveller's Guide x3 & "Sour Dreams" Soft Candy x2
You can use the code on the Code Redemption portal via your web browser, or directly in-game (by going to "Profile" [Press "ESC" on PC]-> "3 DOTS BUTTON" [Top right] -> "Redemption Code"). Select the server to find your character and it will be sent instantly to the mailbox.
Note: These codes may expire quicker than I have listed as there is no known expiry time that i can find.