A direction to pay a specified amount to ‘B’ and not to anyone else is

Under Section 13 of the Negotiable Instruments Act, 1881, a negotiable instrument is a promissory note, bill of exchange or cheque payable either to order or to bearer. An instrument payable to a particular person is payable to order only if it does not contain words prohibiting transfer, so a direction to pay B "and not to anyone else" is not negotiable. It is not a guarantee or a promise either, because it is an order to pay, not an undertaking.