I will only answer the first one.
1. Almost all luxury cars imported from UK or Japan have their odometers rolled back.
In both cases, the IMPORTER, in our case Pakistani does it. In case of Japanese auction houses like USS and others, they cannot and will not do it as it's illegal to do so in Japan. Most reputable non-Pakistani owned Japanese Exporters (middlemen), who are registered in Japan to bid and buy auctioned cards on behalf of customers cannot tamper the mileage by law, else their registration can be reported and cancelled.
Therefore, you will only see this being done by native Pakistani Japanese car exporters (at least for the cars exported to Pakistan) sitting in Japan who buy cars from auction houses in Japan to export to local dealers sitting in various cities of Pakistan, such as on Khalid Bin Waleed road, Jail Road, Defence Main Boulevard etc. Most of these middlemen dealers in Japan and car dealers in Pakistan are relatives of dealers sitting in Pakistan and run these businesses on joint-venture basis. Hence, they do these activities knowingly and never get reported to local authorities in Japan for prosecution.
In case of UK vehicles, it's really easy to check the accurate mileage and history of car prior to buying from the open market. However, all cars imported from UK by dealers are high mileage cars which are later tempered and then exported to Pakistan for sale.
In either cases, you can safeguard yourself from buying a tempered mileage car by self-importing one.