Monitoring FPGA using vendor provided library APIs

First do not multipost, asking your question once is enough.

Second what you need to monitor depends on what you put in the FPGA. An FPGA by itself doesn't have cores, fan control, and AFAIK the Stratix FPGAs are the only ones from Altera that have a temperature sensor.

There is no vendor API, as you are responsible for what you program in the FPGA. It is up to you to add both the hardware and the software functions you need to monitor your application.