This is a rules decision, not an interface limitation. You may or may not like it, but it is that way on purpose...
Suprised to learn that. What can be the rationale for that? Honestly, it doesn't seem to make any sense, if you've already decided on how to proceed, it should be your right to do so (and your problem if you blunder).
This right here is why I prefer other chess sites for very fast play. Just watch some of Benjamin Finegold's stream/videos for an example of how this works.
That's not true. You can do conditional premoves on the analysis board.
That is only true for correspondence games. For other time controls you can only make a single premove.