No
No. All flies are invertebrates, just as all arthropods are invertebrates. These creatures do not have backbones.
Yes, this is the way a fly has to eat.
Your question should be "Does a housefly eat insects?" or "Do houseflies eat insects?" Whatever your question may be, the answer is no.
Tarantulas will eat crickets, moths, beetle larvae (meal worms or superworms), houseflies and cockroaches.
There are no houseflies in Alaska.
Houseflies are born from maggots.
Houseflies eat sugar, decaying animals, spoiled eggs, food and flesh.
The family that common houseflies come from are Muscidae.
The houseflies enemies, other than the human, are spiders.
Houseflies can take in only liquid foods. They spit out saliva on solid foods to predigest it, and then suck it back inside. They also regurgitate partly digested matter and pass it again to the abdomen.
Nowhere. There are plenty of houseflies still in Australia.