Very software out there has a limit for character but I haven't seen any such limit for a post in WordPress. So I need to know if there is actually a Max character limit for a post in WordPress or not? If there is then what's the limit?
If you check the database description you'll see that the post content column is
longtext, which is:
A TEXT column with a maximum length of 4,294,967,295 or 4GB (232 − 1) characters. The effective maximum length is less if the value contains multibyte characters. The effective maximum length of LONGTEXT columns also depends on the configured maximum packet size in the client/server protocol and available memory. Each LONGTEXT value is stored using a 4-byte length prefix that indicates the number of bytes in the value.
You will more likely run out of usable memory before the max character length becomes an issue.