In summary in my code:
Users findFirstByUsernameOrderByUsername(String username); // builds
Users user = repo.findFirstByUsernameOrderByUsername(username); // builds
Users findFirstByUsernameOrderByUsernameAsc(String username); // builds
Users user = repo.findFirstByUsernameOrderByUsernameAsc(username); // builds
Users findFirstByOrderByUsernameAsc(); // builds // not accepting any parameter inside brackets
Users user = repo.findFirstByOrderByUsernameAsc(); // builds
Users findFirstByOrderByUsernameAsc(String username); // fails to build
Users user = repo.findFirstByOrderByUsernameAsc(username); // fails to build
The error "At least 1 parameter(s) provided but only 0 parameter(s) present in query":
"Parameter" here means Username inside the method name,
not the parameter inside brackets.