'Any' is so closely related to the negative that I teach it as meaning 'not none' which can be broken down further (but is less intuitive as) 'not not one'
The subtler point is that if I will accept ANY kind of ice cream, ALL kinds of ice cream are acceptable, as long as they are ice cream
in No. 1 then, 'anything' and 'everything' are interchangeable, because EVERYTHING that comes up is SOMETHING, ie: NOT NO-THING, which equals ANY-THING.
For all the phrases in No. 2, you can paraphrase using 'everything,' although it sometimes makes an akward sentence:
Everything that has wheat in it will make him sick if he eats it.
Please tell me everything there is that I can do to help.
::note that this is not a good paraphrase
::For one, it is a command and not a question, and even so
::we should use SOMETHING::
Is there something I can do to help?
Please tell me if there is something I can do to help.
::because EVERYTHING, unlike ANY, is always a totality.
Let me know everything that happens.
:: again, easier to do with SOMETHING
Everything that I know about computers, I've learnt in this job.
:: Here, it is not easy to use SOMETHING, notice that
:: NOT ANYTHING == NOT NOT NO THING == Absolutely Nothing!!
:: So not absolutely nothing is everything.
To your final question: No, the meaning of ANY never ever changes (any!), but its usage in compound words, questions, and negatives make it hard to understand, and in addition, it is itself a negative compound of NOT NONE.
Good luck with EVERYTHING you do. Post back if there is ANYTHING that you dont understand about this. ANY and EVERY time that I can help, I like to try.
Student or Learner