In Hearts, impossible to play first hand?
Both the rules about not leading a point card until hearts have been broken, and not being allowed to lead a point card, are not applicable if you have no other choice.

There's no one official rulebook to point to for hearts, like most other card games. But various sources such as here and here all say the same thing:


  There are two exceptions to play to be aware of:
  
  
    You may not play a point (a Heart or ♠Q) on the first trick of a hand
    
    You may not lead a point card until a Heart or ♠Q has been dumped on a prior trick (a game option can change this to only a Heart being dumped; see Options, below)
    
    In each case, you may play or lead a point if you have no alternative.
  


You do not have to show your hand to "prove" that this is the case; Hearts, like most card games, often has restrictions on what you can play (you must follow suit if you can); yet when you can't follow suit you don't show your hand to prove that your play was legal. If you illegally play this way, players will likely notice later when you play a different card that you should have played previously.

Also, it is worth noting that the rule about not being allowed to play a point card on the first trick of a hand is not universally used. It is not mentioned at all on some Hearts rules pages, and the second link I provided above mentions it as


  Some play that is illegal to play points on the very first trick, unless of course you have you have nothing but penalty cards in your hand.