How to make specifics apps password protected even after passcode in iPhone?
no, this is not possible, sorry
While there is no way to get this functionality "out of the box", you can take advantage of "Restrictions" to accomplish what you want.
In the Settings App, tap General, then Restrictions. You can Enable Restrictions and then Don't Allow Any Apps. It's not as convenient, as you have to go through some menus, but it should work.