Can I purchase ICOs through Coinbase or any other exchange site? How does purchasing ICOs work?
-D
Do not do this. Most ICO's reward the tokens back to (for example) your ethereum adress, which means they'll be in possesion of coinbase, where you don't have control over your private keys, nor your tokens.
Consequently, private keys associated with a specific address are virtually inaccessible outside of extremely limited circumstances.
https://support.coinbase.com/customer/en/portal/articles/2829461-altcoins-and-icosAlthough i guess it could work for some ICO's where they don't reward the tokens back to the adress you send them from, but rather an adress on their blockchain or something. i'd really look this through before doing it though!