1. There are many floating around the internet. Just make sure you check their legitimacy first. For Bitcoin specifically, I'd recommend Electrum, which you can use as an offline wallet by following these instructions: http://docs.electrum.org/en/latest/coldstorage.html

2. Yes. It's much harder to take coins out of them after all. You normally have to go through a number of hoops, so the same goes for any potential hacker.

3. Wallets can typically only hold coins they're designed for. If you want to hold different types of coins in a single wallet, you likely have to use an online one.