What problems can arise if one uses flash devices not listed in PFL IP core ug?

The PFL IP core user guide lists several flash devices that are of CFI, Quad SPI and NAND flash type and should be used with Altera devices. I have the following questions:

(1) Does each Flash memory type have different method to interface with the FPGA. i.e does it use different control signals?

(2) Do Altera FPGAs and CPLDs have specific pins that are used to interface with flash devices? I would expect so for communication purpose.

(3) Can the same flash memory used for configuration also store user data e.g sound files (.wav) or other data required by the design?

(4) What problems can arise if one chooses to use a flash memory device that is still listed as CFI or Quad SPI and manufactured by Micron or Intel however it is not found in the list of the PFL IP Core user guide?