Custom blocks - focus order

Good questions — and good on you for testing with NVDA early. A couple of general rules that apply whatever the block type: a screen reader reads text, not containers, so your number + text will be read as long as they're live text (not baked into the image). If the 1-2-3 graphic is an image with the numbers inside the image file, that won't be read — the numbers need to be live text or have alt text. For the canvas: yes, text placed on it gets read, in DOM order. I haven't tested the custom blocks beta specifically, so verify with NVDA — but those principles hold.