I'm also interested in this. Without those methods, is it only possible to get a sparkling mead if it is dry?
Well, anything's "possible", right? Just not practical......
It would be nice if the yeast stopped EXACTLY at the alcohol limit stated by the manufacturer, but unfortunately that's not the case. If you try and predict where the yeast are going stop fermenting, so you can have a sweet bubbly mead, the yeast can appear to stop early, leaving you with a mead that is sweeter than desired, with little carbonation, and waiting for the right conditions (temperature change, agitation) for fermentation to restart. Or the yeart can continue on past the stated alcohol limit, ferment all the honey, over carbonate the bottles, leaving you with the potential of "bottle bombs".
I've read where people have tried to use pasteurization (heating the bottle and contents in a water bath, between 140F and 190F degrees), to kill the yeast, but from what Ive read this can also lead to problems, where the bottles actually blow during the heating process. There's also the issue of trying to figure out at what point you try and do this procedure (opening and measuring the contents of multiple bottles seems to be the only real way).
Conversely, you could refrigerate all your bottles, once they've reached the desired carbonation and sweetness level (more opening and measuring), causing the yeast to go dormant, but you would need to keep them refrigerated until consumed, as refermentation could easily resume once they are warmed. This not only requires permanent refrigeration space, but means you should not be giving any of your mead away to unsuspecting friends or relatives.
So, possible, but not practical.........