Can insured and beneficiary be same on life insurance?

Well, in practice, I hope you see the problem with this arrangement: by the time it matters who the beneficiary is, the insured is dead. This presents a conundrum.
Legally, any property of the deceased ... including, I suppose, life insurance benefits ... would become the property of the deceased's estate, and that would be distributed according to the will and/or relevant law. So it's not an insurmountable problem.

It is more often best that the beneficiary be someone other than the insured. Whenever possible, it is best to keep assets out of your estate.