Hi Satoshi-san,
1. For POR, difference between the TMP100 and the TMP102 is as follows.
TMP100 invokes POR when VDD is lower than 0.3V with 100ms or more.
TMP102 invokes POR when VDD is low in short time even 1usec.
2. The TMP102 uses newer core than that of the TMP100. It has improved accuracy, lower supply voltage, and lower Iq as data shown in the spec sheet.
3. When you do not use ALERT function, ALERT pin should NC. Although ALERT pin is an open drain circuit we strongly recommend to be NC, when it is not used.
Best regards,
Ichiro Itoi