2. The problem with being able to get your money back when you make a mistake is that you can also get your money back when you don't. It enables the kind of serious fraud that banks and credit card companies have to deal with. If you need a third-party to validate transactions, then you have eliminated the main advantage of a cryptocurrency.
It seems like what you are asking for is a banking system and debit cards. That has all the features you want and it already exists.
Not a third party, but the wallet itself, something similar to checksum which shows that is valid by have a check on the transaction history.
Check address 321
Owner address | 321 Address
Transaction History | Transaction History
Check Function sent 0.001 | Received 0.001 from xxxx (check function)
to address 321 | Sending 0.001 to xxxx
Received from 321 Check |
function complete |