After I go to sea of moving ice and icasracht’s lair…. Can I come back to lonelywood……. So many good items to buy there but I don’t hav ethe money….

Sorry - but no. You can't leave until I dies - and that ends the game

(unless you haven't yet completed IWD - in which case you can go back after killing I.)

i can go back where? kuldahar or lonelywood?

Once you go to the sea of moving ice, you can NOT return to Lonelywood. If you are playing the expansion only game, killing Big I ends the game. If you are playing HOW where you entered the HOW areas from an ongoing IWD game, then you are returned to Kuldahar and can finish the remaining parts of IWD.