update -C question

[Lemke, Michael IZ/HZA-IE5]

Though having worked with cvs for quite a while I am not sure
how to get out of this:

Working copy is at HEAD revision.  Then I do 

  cvs up -r SOME_TAG.

To get back to the HEAD rev I need a 

  cvs up -C.

But will this not also clear any kb options?  If so, then 
how to revert the checkout on the tag?


I also noticed that

 cvs up -j TAG2 -j TAG1

where TAG2 is the same as HEAD cannot be undone with

 cvs up -j TAG1 -j TAG2

Instead cvs says file locally modified.  But it seems that
when TAG2 is not HEAD the above works (modulo conflicts).
Correct?  Comments?

Thanks,
Michael