Sealed class for Repository to ViewModel comunication

Question

Based on this post by Florina Muntenescu I have 2 questions:

Question 1: In the following situation considering a Respository response SomeApiResult:

sealed class SomeApiResult<out T : Any> {
    object Success : SomeApiResult<Unit>()
    object NoAccount : SomeApiResult<Unit>()
    sealed class Error(val exception: Exception) : SomeApiResult<Nothing>() {
        class Generic(exception: Exception) : Error(exception)
        class Error1(exception: Exception) : Error(exception)
        class Error2(exception: Exception) : Error(exception)
        class Error3(exception: Exception) : Error(exception)
    }
} 

Latter when using when in my ViewModel I wont be able to do something like:

when (result: SomeApiResult) {
    ...
    is SomeApiResult.Error.Error1,
    is SomeApiResult.Error.Error2 -> {
        // it will fail with "Unresolved reference: exception"
        result.exception
    }
    is SomeApiResult.Error.Error3 -> {
        ...
    }
}

How can I solve this?
This is valid though:

when (result: Result<Int>) {
   ...
   is SomeApiResult.Error -> result.exception.message
}

Question 2: When creating the error response I have to create a GenericError because if I try to instantiate the sealed class I get an error. This is how I make it work:

is Result.Error ->
    when (result.exception) {
        is Error1 -> SomeApiResult.Error.Error1(result.exception)
        is Error2 -> SomeApiResult.Error.Error2(result.exception)
        ...
        else -> SomeApiResult.Error.Generic(result.exception)
    }

In my ViewModel I wont be querying for Error.Generic.
Instead, I'll use is SomeApiResult.Error as shown above (like else -> "other errors"). Is this the right way?