#1 should really say, "Avoid new and delete." new and delete are for experts. The average C++ programmer should go nowhere near them. If heap memory is used internally by a class that was written by someone who knew what they were doing, then fine. Use your std::vector. But new and delete are huge red flags in code.
It's fine to use new as long as you're immediately sticking the result in a smart pointer. But yes, delete should be very very rare in modern C++ code.
It depends. The trick to using new correctly is to put it in a function whose sole purpose is to immediately store new's result in the smart handle. I.E. You're writing a function that's analogous to the make_unique function.
You might need to do this if you're implementing your own smart handle or writing a factory function for a class with a private constructor (make_unique will not work).
Off the top of my head, I can't think of any good reasons to use delete.
If your handles are pointer types, you should still use unique_ptr, you just need to give it a custom "deleter". (Of course you should probably still encapsulate this in a function like make_xxx() just to avoid the potential mistake of not supplying the correct deleter everywhere.)
and yet, "new" and "delete" are amongst the very first things covered in every C++ tutorial book.
for example in Stroustrup's "A tour of C++", it's covered in section 1.6. without any remark about shared_ptr and friends.
