Thanks for your inquiry. For the second question, I confirmed that D9 and D17 are both CRX0. Let’s check the XIAO RA4M1 pinout sheet, XIAO RA4M1 schematic and RA4M1 chip datasheet together:
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In XIAO RA4M1 pinout sheet, D9 = P110 = CRX0, D17 = P102 = CRX0.
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In XIAO RA4M1 schematic, (Position of) D9 = P110, (Position of) D17 = P102. Please notice that the 8 pins on the backside is horizontally reversed in the schematic because everything on it are looked from the same direction.
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https://www.renesas.com/en/document/dst/ra4m1-group-datasheet
In RA4M1 chip datasheet, we can see that P110 and P102 are indeed CRX0.