Bitcoin block maturity and block reward rules

Question

According to the Bitcoin wiki:

"When a block becomes an orphan block, all of its valid transactions are re-added to the pool of queued transactions and will be included in another block. The 50 BTC reward for the orphan block will be lost, which is why a network-enforced 100-block maturation time for generations exists."

Ok, so let's say at block height X, two miners produce separate valid blocks - block A and block B. The miners compete with each other to mine on top of these two blocks. Eventually, the chain with block A becomes the longest chain, and thus block B becomes orphaned. However, the chain with block B is more than 100 blocks long (despite it being the shorter chain). Does this mean that, despite block B being orphaned, the miner who mined block B can still spend the block reward?

In addition, consider another scenario: a miner goes back to a previously orphaned block (a block that was orphaned in, say, 2 months ago) and starts mining on top of it. He produces a chain that is 150 blocks long. Although this chain is still shorter than the main chain, according to the 100-block maturation rule, the miner can spend the block rewards of the first 50 blocks of this 150-block orphan chain, right?

I know the scenarios I suggested above are very unlikely to happen in reality, but I'm just curious.......

Answer 1

Split chains can be seen as separate coins, except that a transaction with inputs valid in both chains (maybe a coinbase before the fork) would be valid in both. In that miner's chain, the miner can spend his coinbase. The rest of the nodes will see the transaction as invalid and ignore it, as his block isn't part of the main chain. If the miner wants, the miner can advertise his chain as a "new coin", referencing the first block that is not common, and nodes who would be built to recognize his chain would allow the miner to spend the coinbase transaction.

In the second scenario, the same thing happens. What he does is well-received in his chain, but ignored in the main chain (the chain with the largest proof-of-work)

Answer 2

The block reward of a Bitcoin block is paid out in the first transaction of a block, the coinbase transaction. In Bitcoin, you can only spend bitcoins when you own an Unspent Transaction Output (UTXO) that is part of the current UTXO Set. Since the output of the extinct block's coinbase transaction only exists on the extinct chaintip and doesn't exist on the best chain, it is not spendable on the best chain.