How to get BIP34Hash and nMinimumChainWork?
The BIP 34 hash is the block hash at which BIP 34 was fully activated and all blocks less than version 2 were rejected as invalid.

nMinimumChainWork is a value that is updated at every release. It is retrieved from the getblockchaininfo RPC of a node that is up at the time of release. nMinimumChainWork is updated at the same time as assumevalid. It is calculated by summing the work done in each block which is calculated by doing 2^256/(target+1)