Demand Promissory Note

Nothinng forbids a private company incorporated under the Indian Companies Act of 1956 from executing such a promisory noted if the articlesof association and memorundum of association permits whenmade along with the Board resolution 

Since it  being an incorporated personality with no life or limb, the directors of the company who act for and behalf of the company are to be demanded payment, may be  from the registered office the demand is to be made either orally or despatching the written demand addressed to the company to the registered office

yes, a demand promissory note can be exucutable by any person or firm or by a body incorporated, as per the negotiable instrument act