If a person is "hard of hearing" it means they find it hard to hear things, they either have a congenital hearing problem or for some reason (eg age, disease or industrial injury) they are going deaf.
"Hard of hearing" is an idiom used to describe a person who has some level of hearing loss or difficulty hearing. It is often used to indicate that someone may have trouble hearing or understanding what is being said.
To complain or criticise someone out of their hearing.
Life Is Sometimes Hard
The idiom "a nut to crack" has the basic meaning of "a problem to solve." Some "nuts" are hard to "crack," while others are easy, but this can only be determined by context.
"To be" is not an idiom - it's a verb.
The meaning of the idiom "to slap the back off you" is fairly straightforward. It implies an exaggeration, that one would slap someone else so hard that their back would come off.
Perhaps you mean "crack you up." This is an idiom meaning to make you laugh a lot. The image is of you laughing so hard that you crack apart.
That would be "crack you up" - the image is of you laughing so hard that your sides crack open.
Pest is not an idiom. It's a word.
The idiom "apple shiner" means the teacher's pet.
The meaning of the idiom in the pink of health means being in good health.
The idiom means impress someone is egg on