For all intents and purposes, they are. None of Apple's SoCs since the A6 (2012) have been based on ARM's Cortex-A cores; the CPU design is fully in-house at this point.
Yes, but the M1 is nothing like a new product. As you indicated, Apple's first custom SoC was released in 2010, 11 years ago. They have >10 years of experience shipping SoCs for Apple products. The M1 family can be viewed, to some extent, as an extension of the work on the Ax chips, which likely builds on their experience customizing chips for the iPod family.
Yes, but the M1 is nothing like a new product. As you indicated, Apple's first custom SoC was released in 2010, 11 years ago. They have >10 years of experience shipping SoCs for Apple products. The M1 family can be viewed, to some extent, as an extension of the work on the Ax chips, which likely builds on their experience customizing chips for the iPod family.