1. Whilst it is predicted that 'whom' and its variants (whomever,whomsoever) will disappear from English this century, currently it is still regarded as essential for correct, grammatical English.
2. a 'regulation' is a rule or directive made and maintained by an authority, whereas a 'custom' is a traditional and widely accepted way of behaving or doing something in a country.
It may be a social custom to use chopsticks in your country. If it were a 'social regulation', then the moment I pulled out my own knife and fork, the manager in the restaurant would call the police. It would be the same as smoking in a restaurant in Britain: it is not a social custom not to do so, but a regulation (a law).