how can i get a Christmas flower. i need a Christmas mouse to finish my game.  or how do i delete the christmas one to catch something else

The ice flowers are no longer in season, but there a couple options:
1. pause the quest and finish next year when the ice flowers are back
2. pause the quest, then restart it - that will allow you to change the wildlife you are attracting
3. if you have a festive tree or snowman in storage and star dust, you can put it in your garden, star dust it, and it will snow again

If you have a Christmas tree or a snowman (not a Santa) stored you can bring that back into the garden then use a stardust to start it snowing in your garden again - this will change mice and ducks to festive critters again while it is snowing.  If you don’t have these stored or cannot/don’t want to use a stardust you will have to either pause the quest until next year (only if an ordinary quest not a pottery lottery quest) or cancel the quest and start again. 

Have you got an unfinished tree or snowman? There are gardens where you can spot what you need to finish it and that will give you three days.
(I deliberately save some that only need baubles or gifts and these are easier to get even without it snowing)

can anyone trade a stardust with me  i need one

You can’t trade a star dust, to be able to get star dust you need to purchase gold it’s the only way X