A coinbase transaction it not spendable till it’s 100 blocks deep within the blockchain. Since a block is produced each 10 minutes, it can sometimes take 1,000 minutes (slightly below 17 hours) earlier than a miner can spend the reward.
1). Does the miner get rewarded as soon as 51% nodes settle for the block? In that case, how is that acceptance info propagated to his/her personal node – is it finished as and when every node within the community accepts it?
It is 51% of mining energy, not nodes. As soon as 51% of mining energy is mining on high of the block, it can proceed to get longer at a sooner price than another blockchain, guaranteeing it’s finally 100 blocks deep. (This isn’t actually 100% assured, but it surely works this manner the overwhelming majority of the time.)
2). Or does the miner get rewarded the second he/she creates a block and broadcasts to friends? In that case, how is the reward reverted if the block is discovered to be invalid?
The reward is reverted if the block is discovered to be invalid as a result of the reward was in that block. So any node that does not think about that block legitimate will not think about a transaction to spend the reward legitimate. To ensure that a transaction that spends the reward to be thought-about legitimate, the reward itself have to be thought-about legitimate and the block by which the reward was rewarded have to be 100 blocks (or extra) deep.
