Let’s talk about Merkle trees.
To prove that a transaction is included in a particular block, you only need a small number of hashes along the path from that transaction to the Merkle root. The number grows logarithmically with the number of transactions.
Honestly, I only understood this later: light wallets rely on data from the nodes they connect to, and large incoming payments can be cross-checked using several block explorers.
The header of every $BTC block contains a Merkle root corresponding to all the transactions in that block.
When you see claims of stable, high returns, be skeptical.

#BTC

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