Yes, it's used to make comparisons. You can also write it as ...더 뜨겁습니다 or without the 더
Yes, 보다 means "more than" whatever it is attached to... It is a suffix attached to the end of the object.
Not sure if this helps but to my understanding 음식 means 'food' 음식보다 means 'than food'
cheap+ food + expensive+than food+is hot = Cheap food is hotter than expensive food. ?! I would like that someone explain me the structure of the sentence and why the words are put this way ?