But is it possible to mine those with a USB bitcoin miner?
Someone on this forum told me Bitcoin miners can mine bitcoin only.
I know all these USB miners can't generate any profit at all if you mine Bitcoin or other popular currencies.
S9 has TB hash rate... these USB miners barely have one or two GB rate. If one S9 is not enough to generate good amount of money, USBs can't battle in the mining pool.
Yes, correct. Any ASIC is specific to the algorithm, so a "bitcoin" miner can only mine SHA256 coins, a "litecoin" miner can only mine scrypt coins, a "dash" miner can only mine x11, etc. ASIC stands for Application Specific Integrated Circuit.
You CAN use USB ASICS, but most of them have the same limitations as their louder, more expensive brethren. If you want to mine obscure coins your best bet is to make a small build computer with one or two cheap GPUs on it, it will give you the widest range of coins to choose from. You can build a single card miner for probably around $300 or so, or less if you use parts you already have/pick up at a second hand store/etc.