Pumping Moms!

Alexis • 25, momma to a little boy, 3 years old, diagnosed with Angelman Syndrome in Nov. 2017, living life to the fullest! 💙 11th cycle TTC baby #2! 💝
Once breastmilk has been pumped how long is it good for at room temp? 
If breastmilk as been in the fridge and then warmed how long is it then good for a room temp?
This is probably a silly question if I'm out in public and I have it in a cooler and he gets hungry and there is no where to warm it, do I still give it to him? It would be too cold? 
FTM just trying to learn about exclusively pumping and wondering for when I start taking my little man out places!