Regarding differences between 24FC1025-I/P and 24FC1026-I/P; (25 Vs 26), please see below product manager’s response:
“Looks like they have a slightly different pin out”
26 suffix, check page 6: https://ww1.microchip.com/downloads/en/DeviceDoc/20002270E.pdf
25 suffix, check page 5: https://ww1.microchip.com/downloads/en/DeviceDoc/20001941L.pdf
Summary
24FC1026-I/P-ND
24FC1026-I/P
IC EEPROM 1MBIT I2C 1MHZ 8DIP
24FC1026IP
24FC1025-I/P-ND
24FC1025-I/P
24FC1025IP