According to your experience what altcoin is good to hold for long period? and where to hold it ?
Litecoin, Ethereum, Ripple, Monero.
Here's a site that lists all coins, wallets, and exchanges. If you got a coin you can find out which exchanges support it. If you go to a wallet or exchange you can see which coins they support.
Check it out >>>
https://www.cryptocompare.com/Thanks for the link, this is a useful tool and exactly what I needed.