You're asking questions in a very disorganized manner, which will prevent most people from attempting to answer you. Also, there's an emotional feel to your question - you sound upset that people are avoiding taxes.
This is economics and in economics we often discuss how people behave in the market, whether we like it or not. For instance, socialism, emotionally sounds wonderful, yet anyone who's studied the Soviet Union knows it didn't work ... at all.
Will people avoid taxes? Yes. Do the rich? Yes. Do the poor? Yes. I worked at a bank for a while and we were required to report when we saw suspicious behavior of customers and I can tell you about the number of times I reported to my manager Americans who collected disability or unemployment while also working for people in cash - they were getting free money from the government, but working for people in cash and not reporting the cash (blatant fraud, which taxpayers funded). For instance, this video, which many think is an embellishment, was not uncommon at all.
For some direct answers:
Bartering is one of the best ways to avoid taxes (as is negotiation) because if the bartering is more financially beneficial than the ease of taxes, a person may barter instead of paying income that was taxed. Anyone, of any class, can barter. To prevent bartering, an economic system wants the tax system to be arranged in a way that would make bartering more costly than just paying taxes.
Charity scams will be favored by the rich, and no the IRS can't audit every charity, even if it's a multi million dollar charity. It can only audit some and hope that deters the others; also, some charities, like the Susan G. Komen foundation, might not be audited because the IRS would fear something else, like being accused of sexism, so billionaires would probably choose politically correct charities, knowing they could get the media on their side and the IRS wouldn't touch them (if billionaires were to go this route).
Getting free stuff? Any class can do this; this is really negotiation. Most international people, who live or visit the US, negotiate and it makes sense. Yes, the IRS loses money, but at the end of the day, it's the rational economic decision.
Also, things like cryptocurrencies (speculation) are ways the rich avoid taxes, as well as buying assets privately held in other countries (see the Chinese bureaucrats as examples). The rich have many more ways to avoid taxes than the poor and middle class, though the other two income categories can avoid taxes as well.
Economically, a simple and fair tax system is the best way to prevent all of this. No one wants to avoid something they perceive as easy and fair. What you're seeing is that some don't think this about the U.S. system, whether any of us in particular agree or disagree.