Regarding Requirements for Unlocking the new Classes Heavensward

[WellFooled]

I have another question if you have one character on your account who has met these requirements can you create a new character who starts off as one of the new classes

I'm afraid not. The new character won't have access to Ishgard without also completing the main story quest of 2.55.

[Keydah]

I have another question if you have one character on your account who has met these requirements can you create a new character who starts off as one of the new classes

No. All characters are completely separate, because there are very few reasons to have multiple characters.

[Felis]

I have another question if you have one character on your account who has met these requirements can you create a new character who starts off as one of the new classes

Every character is like an own savefile and creating a new character like clicking on "new game" in the offline games.
In short, every character start at the very beginning.