This query has already been addressed in the tech support case. I am pasting answer for your queries again below,
Q)What does the number "104" ?
A) Dash number means custom configuration. So, 104 is a factory pre configured.
Q)Can I replace CY2291SC-104 on chip CY2291FX ?
A) No, you cannot replace.
Please let us know if you have any further queries.
Thanks and Regards,