1. If you are a rightful purchaser and a registered sale deed was executed on your name by the vendor properly then there is no question of benami property.
You should ask the vendor that why it has been mentioned as benami while purchased the property by passing the sale consideration amount from your side.
There is no reason for declaring the property as benami when you have purchased it.
2. The POA agent has sold the property on behalf of the vendor is legally valid but the POA deed should have been a registered deed.
3. You send a legal notice to the vendor to clear this obstruction immediately or cancel the booking
4. It depends on the circumstances and hardships convinced by you.