When you encrypt in Salesforce using the encryptWithManagedIV method the first 16 bytes of the returned blob is the IV value the remaining bytes are the phase content. The following C# code will decrypt your example. Using the code below decrypting string returned "info string to be decrypted". Hopefully, this resolves your issue. It appears as though CryptoStream handles the padding issue correctly. Full solution:
byte Key = Convert.FromBase64String("Ii7oSjjWuhp6J6/hj/wmivqx1h3N2HzJ2ByJOy1n89E=");
string encryptedbase64Password = "hRVlbM79aEQi8Tz7JJIL7CEhSxZAJvCh8Ni6ORP1C55+qbJzjDshBYBjyP12/zT2";
byte IV = new byte;
byte phase = Convert.FromBase64String(encryptedbase64Password);
Array.Copy(phase, 0, IV, 0, IV.Length);
byte cipherText = new byte[phase.Length - 16];;
Array.Copy(phase, 16, cipherText, 0, cipherText.Length);
using (AesManaged aesAlg = new AesManaged())
aesAlg.KeySize = 256;
aesAlg.Mode = CipherMode.CBC;
aesAlg.Padding = PaddingMode.PKCS7;
aesAlg.Key = Key;
aesAlg.IV = IV;
// Create a decryptor to perform the stream transform.
// NOTE: This is the difference between my original solution and the correct one.
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
// Create the streams used for decryption.
using (MemoryStream msDecrypt = new MemoryStream(cipherText))
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
// Read the decrypted bytes from the decrypting stream and place them in a string.
plaintext = srDecrypt.ReadToEnd();