Is possible for my Dad to get his license back after they were revoked due to dementia?

If he doctor shops and lies enough he might get someone to say he can drive - DMV regs in each state vary, but usually if a referral is made they have to appear and be assessed to some degree. Getting a completely revoked license back should not be easy though. So, can he be referred for a BTW specialized occupational therapy assessment, or is he so bad even that is too risky? And how is he getting around to see all these doctors if he is not driving?

Nope. I believe, no matter which state, he'll have to pass a driver's test. Those tests are difficult for those with comprehension problems.