No. The Canon R5C features an internal active cooling fan system that allows for non-stop, unlimited recording in 8K/60p and 4K/120p without the overheating issues found in the standard EOS R5.
It uses the LP-E6NH battery. For 8K/60p RAW recording, it is highly recommended to use an external USB-C Power Delivery (PD) source or a dummy battery to ensure the lens iris and high frame rates function correctly.
Yes, by using the EF-EOS R Mount Adapter, you can use the full range of Canon EF and EF-S lenses with complete autofocus and metadata support.
The R5C is dust and moisture-resistant, featuring weather-sealing similar to the EOS R5. However, because of the active cooling vents, it is not fully waterproof and should be protected in heavy rain.