Difference between serial, serial-8051, Ser-uP, SPI & QSPI

The difference between what? We're not mind readers (well, there are a couple of trolls who aspire to psychicity, but they can usually be dismissed); we need more information about what you're trying to compare. Time was, RS sold a house-numbered TI 8-pin ADC with serial output, and their data sheet gave circuits for interfacing to several different micros. The interface was 2 or 3 lines, like enable, clock, & data. Other ADCs, like the 1408 or DAC-08, have a straight 8-bit binary output, so you'd read its output with one input command (i.e., no bit-banging.)

H> When looking at ADC chips that I am trying to hookup to a 8051 I see