1.0 In the whole history of a blockchain, how can we prove which KV pairs were created/updated at which blocks?
2.0 How to store such a Merkle tree
3.0 How to prove a KV-pair is up-to-date? In other words, since some height H, an KV-pair is left untouched (not changed or deleted).
4.0 Should we build a dedicated Merkle tree for these ActiveBits?
5.0 How to prune the ActiveBits and entries?
6.0 How to provide non-existence proof? That is, we want to prove there are no other key(s) residing between key A and key B.
7.0 How to proof a KV pair at any height? Even if at this height nothing happens on this KV pair.
8.0 What are the possible statuses of twigs.
9.0 How to query a KV pair fast?
10.0 How to prune the inactive twigs?