What is the maximum number of dental x-rays that u can receive in a year?

Depends. Most dental plans allow a full mouth set every 3-5 years and bite wings once a year. They also allow periapical views as needed provided they are not billed with a full mouth series. Now the real answer to your question is as many as reasonably needed to make a proper diagnoses. If you have a low risk for dental disease then you should not need as many xrays as someone with a high risk.
Wrong question. All x-rays added together have cumulative toxicity, long-term carcinogenicity. Avoid unecessary x-rays whenever possible. Drs. And dentists with there personal machines look at these devices as a way to print money.