Bitcoin integration

I need a developer to integrate bitcoin payment in a website but the payment system has 2 features: 1 - the buyer can use his BTC address used for transaction to see the username and password required for download. So he will insert his BTC address into an input field and in case if his BTC transaction is 3/3 confirmed (but also check if the price was not modified to pay less than it is the real price + check if the beneficiary was me + check if he paid for the right product ) , so if everything is correct than it will appear a DIV square with his "username and password required for download" (the username and password is taken from database). If it is an error (maybe not 3/3 confirmations, or maybe trying to change the value of BTC ) then it will appear a DIV with an error "something went wrong" 2 - If everything is correct, the buyer's btc address is inserted into a database but after 3 days it will disappear, so the buyer has 3 days to see his username and password after his transaction is confirmed.