As cryptocurrencies are rather new compared to most assets, there hasn't been a lot of specific guidance for a lot of situation, but in 2014 the IRS announced that it published guidance in Notice 2014-21. I'm not aware of further guidance that has been published beyond that, though it wouldn't surprise me if treatments changed over time.
In that notice, the answer to the first question describes the general treatment:
For federal tax purposes, virtual currency is treated as property.
Crypto Taxes EXPLAINED! Bitcoin/Altcoins, Like-Kind Exchanges, Examples! (U.S. Specific Dec. 2017)
General tax principles applicable to property transactions apply to transactions using virtual currency.
Your specific questions (about what constitutes a "business", and when you're considered to be "selling" the cryptoproperty) are likely to be considered on a case by case basis by the IRS. As the amounts involved here are so small (relatively speaking), my recommendation would be to read through what the IRS has published carefully, make reasonable assumptions about what scenarios that are described are closest to what you're doing, and document doing so clearly as part of your tax preparations.
And when in doubt, erring on the side of whichever option incurs more tax is unlikely to be objected to by them.
Of course, I'm not a lawyer or tax advisor, I'm a stranger on the Internet, so for "real" advice you should contact somebody qualified.
I doubt you'd be faulted too much for not doing so given the amounts involved. You could also attempt contacting a local IRS office or calling them with your specific questions, and they may be able to provide more specific guidance tailored to you, though doing so may not save you from an auditor deciding something differently if they were to examine your return later.
There are also phone numbers to contact specific people listed at the end of Notice 2014-21; you could try calling them as well.