Will it be possible to send btc directly from bittrex to participate in the ico ?
Never ever do this. You dont have the private key of your BTC on Bittrex. Just send them to a wallet and then send them to Electroneum.
I will also spend 10 BTC on this ICO.
on the eletroneum website the guide says to send it straight from an exchange wallet. i think once the ICO is done you can just withdraw it to any address of your choosing