Each facility has its own rules and would answer your question to their technical satisfaction and according to their preference. I prefer patients having their gallbladder evaluated to fast at least 2-4 fasting hours. Fasting is irrelevant for a chest CT, if you are not receiving IV contrast and you are not being worked up for an esophageal abnormality but specifics regarding what the chest MR is for is important to know. Best to ask the facility doing the exam.

Depends on area being scanned. Ask your doctor

In general eating does not affect your routine MRI scan