If the milk is too hot, can I rinse the bottle under tap to cool faster? BM and FM. TIA

No issue with that though. However, please try not to overheat the BM as the nutrients will be lost if you overheat the milk. It will be like drinking water to make the baby full with no nutrients at all. You may wish to test the water 1st before putting the formula inside so that you know the temperature beforehand.