1. The word crypto isn't trademarked, nor is Bitcoin. If anyone could do something with "Bitcoin", maybe the anonymous founder(s) would qualify, who has never publicly revealed himself (themselves). However, "some" crypto companies do have them
https://trademarks.justia.com/866/34/ethereum-86634529.html
2. Sometimes people register "ETH" and "ETHER" styled domains. The likes of "Etherscan" (an Ethereum based block explorer) is an existing company, that "serve" the Ethereum community, with regards to tracking. To operate (and to remain on the safe side), I would assume they've had a conversation with Ethereum, for their approval. Ethereum have an ideology of wanting to be "decentralized" and "free", maybe they accept that side projects may want to aid this cause...I don't know. I have a vague understanding of trademarks, but I do know they're not to be taken lightly, under the vast majority of circumstances. IMO
3. I refer to what I said above
4. UDRP: Uniform Domain Name Dispute Resolution Policy. They offer a route for brand owners to recover domain names, that are confusingly similar to their brand, including those that are victims of typosquatting. The similarity test is the first hurdle that a brand owner faces, under the UDRP