Thanks @Yebubbleman I thought that you has forgot of my question ?. After your post, I documented me about T2 chip. I have find that is some kind of ARM processor that play a role also in video encoding function.Regarding your first question, the answer is in the form of "Universal Binary 2", universal binaries that have both 64-bit Intel code and Apple Silicon code. macOS will see which architecture it's on and load the code for the appropriate architecture. That's how you'll get optimal performance on Apple Silicon (M1) vs. Intel and vice versa.
Regarding your second question, the nitty gritty details can be found here: Apple T2 Security Chip: Security Overview
But the short of it is that the T2 is the start of Apple starting to consolidate Mac logic board components that were previously separate components into a single chip. The T2 didn't have CPU or GPU functions as those were still handled by the Intel CPU (and AMD GPUs on the higher end Macs like the 16" MacBook Pro, iMacs, iMac Pros, and Mac Pros), but the secure enclave, Image Signal processor, audio controller, SSD controller, SMC, and many other components got consolidated into the T2. All of those are now baked into the M1 as well. You just now have the CPU, GPU, RAM, Memory controller in there too along with the introduction of the Neural Engine to the Mac for machine learning. But it's the same idea; take components that either were in separate places on the Mac logic board and integrate them into a System-on-a-Chip (SoC) and have that govern more of the Mac's functionality.
So, now it's clear why Apple Care Support reassured me saying "your Mac has a T2 chip" ...