The clock_divisor and clock_frequency settings are options available only for EPC devices and not for EPCS/EPCQ/EPCQA.
To change the configuration clock, reconfigure the frequency in Quartus® Prime and recompile.
Related FAQs
https://www.macnica.co.jp/business/semiconductor/support/faqs/intel/131045/
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Category: Programming/Configuration
Tool: Quartus® Prime
Device: EPCS/EPCQ/EPCQA