The number of confirmations tells you which block a transaction is in:
0 confirmations: not in a block yet.
1 confirmation: in block number "getblockcount" block.
bitcoin CLI don't have function for view block hash by count number
2 : getblockcount-1
Note that if there is a block chain reorganization which block the transaction is in can change (as can the number of confirmations).
This has already happened?
My dream is somehow to get the checked generator of random numbers based on the bitcoin network. I want use sha256(block hash + txid) for this or something like