Second question, is a transaction with 1 confirmation reversible? What are the chances of 1 confirmation Bitcoin reversible?
The more confirmations a transaction receives, the less probablity it has to be removed from the blockchain.
At the time I am writing this post, Foundry USA is the biggest mining pool with 26% of the total hash power. Assume that Foundry USA turn evil and decide to remove a transaction from the blockchain.
If the transaction has only 1 confirmation, there would be a probability of 54% that Foundry USA manage to remove your transaction from the blockchain.
The probablity would be 34%, if the transaction has 2 confirmations and 22%, if it has 3 confirmations.
If the transaction receives 6 confirmations, the probablity would be 6%.