that's just 3 shamir secret sharings.
replykey is protected by a 3 of 3 keys.
1 protected by 3 of 4 (i.e. SSS the key into a 3 of 4) 1 protected by 2 of 3 (i.e. SSS the key into a 2 of 3) 1 that just is.
so you take your original key and SSS into a 3 of 3.
you take part 1 and SSS into a 3 of 4, and take part 2 and SSS into a 2 of 3.
Yes, but a 3 of 4 SSS is not possible with the linked web page. It's also not user-friendly to expect non-technical users to manually go through multiple rounds of SSS in order to restore the original secret. Ideally it'd just be one page that clearly explains exactly what they need to provide and then restores the secret for them.
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