Is there any really free NFT worth anything?
Mostly they have over-value or zero-value.
Probably we can get many free nft over different platform (not cmc only). But what we can do with them? Is it possible to sold them whenever we want? Or just need to wait something special?
It depends. If you can receive airdrop and assign a specific wallet for it. You can claim airdrop and sell it. I consider it as altcoin airdrop and NFT is just one of airdrop methods.
However, if you have to do KYC and submit your personal identity documents, whatever similar to such, I would recommend you should not do this. In addition, make sure people don't carelessly install wallets, apps from new and zero reputation projects. Claiming a zero-/ low-value NFT and get a breach to hackers, it's terrible.