You cannot just file for citizenship based on your being here for more than 5 years. Generally, for an alien to apply for citizenship, he must have been a green card holder for 5 years ( unless the application is based on marriage to a US citizen, in which case it's 3 years). Although your case was administratively closed due to a grant of PD, you did not state you have become a green card holder. If you are out of status then your employer will not be able to sponsor you for a work related visa unless you get out of the US and come back in. You shoud not leave without seeking advice from an attorney.
Generally, in order to change to a nonimmigrant status or to adjust status someone has to be legally in the U.S. You entered under HP, but it is not clear what, if any, status you have now. You'd want to discuss all of this with an attorney. Generally, for citizenship, you need to be a lawful permanent resident for 5 years prior.
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The business the alien found should hire an experienced immigration attorney as soon as possible. These kinds of petitions cannot be handled by that alien.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.