128 KB Flash, 20 KB RAM, 6 KB EEPROM — memory sizing for the BOM
Supply range and USB — what the 1.65 V minimum means
At the low end, 1.65 V is below the typical 1.8 V floor of many Cortex-M0+ parts, which helps in deeply-discharged battery scenarios. USB connectivity is available on-chip — the part includes a USB peripheral, so a USB device interface (e.g., virtual COM port, HID) can be added without an external PHY. The 25 available I/O pins in the 32-UFQFPN package are enough for a sensor hub or a simple human-machine interface with a small display and a few buttons.
The ROHS3 compliance is confirmed on the manufacturer's documentation.
Design-in checklist: package, supply, and temperature
The internal oscillator is available, but for USB operation an external crystal (typically 8 MHz or 12 MHz) is recommended for accurate bit-rate generation.