Type 1 and Type 2 are different beasts. With Type 1 Diabetes the body stops producing any insulin. With Type 2 Diabetes the body produces insulin of a poor quality, or of a poor quantity, or the body is resistant to the insulin that is made.
It is my understanding that Type 1 happens swiftly, and there's absolutely nothing anyone can do about slowing it's progress. There is no prevention.
Type 2 can hum along slowly for many years (about a decade in my case I think) before diagnosis. It can sometimes be improved or put into remission by weight loss or diet control. Type 2 isn't a borderline form of Type 1.
Diagnosis of Type 2 can be tricky if insulin impairment is only slight. But, I don't believe that diagnosis of Type 1 is as tricky.
The symptoms of both types of diabetes are very similar, and as many members here will tell you, sometimes diagnosis of type is harder than the diagnosis of diabetes.