The pronunciation is actually considered to be the same. "Standardized" Hindi spelling uses the Y in this case, but when the same formation occurs in other languages similar to Hindi, or when spelled by Hindi writers who are not totally familiar with the so-called standard, they may use आएगी. There is no such distinction when Hindi is spelled in Arabic alphabet.
Yes. But the verb conjugation tells you whether it's a female or a male in the context.
वह can mean all of these following:
Hindi actually doesn't have true 3rd person pronouns. So, we use the word for "this/that" (यह/वह), "these/those" (ये/वे) to refer to people also. They actually only mean "this/that/these/those". It's the English translation that forces us to translate it as "he/she/they".