There is no good reason to disallow any particular letter or character at the start of a password.
This sounds like an attempt to stop people from using common "bad" passwords (like making a rule that passwords can't start with a 'p' to stop people from using
password as their password).
To go further though, almost all of these rules disagree with the latest password guidelines from the NIST. In particular, requiring special characters is no longer considered best practice. Rather, the most important rule these days is to simply check against a list of known leaked passwords (which can be easily done using services like haveibeenpwned).
In particular I would point out that the last rule (no repeated characters) sounds good, but in practice decreases entropy of unique random passwords, and therefore actually makes passwords less secure. These kinds of rules are generally recognized as more "security theater" than anything else, and don't actually help users make better passwords.