Issue adding sealed content types having same columns to list

Two known issue regarding content types :

1 ) If you are adding multiple sealed site content types to list and check content type properties from view you will see same default content type attached to every document.It is known issue with sharepoint because it will not recongnised new template at time of attaching content types.
Resolution : if you are doing it using object model then unsealed content type add it to list and then sealed it back at site level.
2) If all sealed content types having same columns then it will be failed again at time of adding all content types at saem time to list(both in GUI and using object model)
Resolution : Add one content type first and then add rest all content types to list will solve the purpose