Hello Ratheesh T,
1. 54102 has Unique ID (UID) or not ?
Yes, LPC54102 have the UID, each chip have different UID number.
2. What is the use of above two section of Read UID for my use? or it has other UID for my usage?
IAP and ISP read UID is just two different ways to get the chip UID. ISP can use the ISP, take an example, UART, and associate with the flash magic software(read device signature) to get the UID. IAP is the command you can used it in the code. Actually, UID is the same, just read method different.
But, please take care, in lpc54102, the errata has some description about it:
http://www.nxp.com/documents/errata_sheet/ES_LPC5410X.pdf

So, just like the workaround, pleas read the flash address directly.
Take an example, I use the JLINK commander to read these bytes:

You also can try it like this, I also use teh LPCXpresso54102 revA, OM13077.
Wish it helps you!
If you still have question, please let me know!
Have a great day,
Kerry
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