Can anyone provide info on what validation checks are performed in the process of providing passport details by the airline to the Govt of the arrival country?
Probably not because, as I mentioned in an earlier post, it's probably classed as confidential.
At a guess, based on what used to be taught in A level ICT - there will probably be a validation check on the passport number (they tend to be 9 characters long). Where an address is needed, like USA, it'll probably check it's a valid address within the territory against the local address database. And other standard data validation checks - names can only contain letters, etc... For the transfer of data, there will be a check digit within the record which the system at both ends uses to make sure the data was transmitted correctly.