Can someone with diabetes do fasting for weight loss??

Not type I without a doctors recommendation. Type II , watch your sugar during your fast if taking meds for it .

You should talk to your doctor it's not advisable do to hypoglycemia

Don’t play with your blood sugar levels. Keep them at the level your doctor recommends. One hypoglycemic event and you could end up with permanent damage.

Yes but it depends on their diet. They can fast if they are on the Keto diet I know that for sure.

My opinion is any dieting or fasting should be approved by your doctor

You might end up in COMA.
Consult a physician and a nutritionist before doing such thing.

I think it would be best to seek a doctors thought on it

You should talk to your doctor about it