Breast milk question

Be

How many times can I warm up my fresh expressed breast milk?

After four hours have gone by (Untouched breast milk) can I store it in the fridge?

When tracking timeframe of fresh expressed breast milk do I start from the beginning or ending of a pumping session?

Once I warm up my fresh expressed breast milk and baby hasn’t touched it how long do I have until it spoils to give it to him?