Before you start attempt to look and recover any data, you should make raw copy of your drive/partition. You also can perform recovery attempt from the raw copy, rather than the drive/partition itself.
Just in case you found note with combination of alphabet and numbers, you could check
https://en.bitcoin.it/wiki/List_of_address_prefixes what hint, information or data you found.
Even if you formatted the drive 10 times, its possible to recover data. You just need to hire a pro.
That depends on how the drive formatted. Normally your statement is correct, but not when
full format performed, where few tool/software write zeros to whole drive before write the file system (NTFS, etx4, etc.)
He is right, there are tools where you can read the drive with a magnetic device, so even a full format and 5 formats, still the data can be read with special hardware