To obtain your private keys you must login to your account and navigate to wallet > backup wallet.
No, there are no restrictions on how many accounts you can have.
Your master key can be found in your security centre. A master key is very important as it is used to recover your password or your wallet ID if you forget it.
No, you can spend funds right away when you receive them.
This can happen if you spend unconfirmed transactions right away, but eventually the funds will be shown on the blockchain. This depends on the miners and we have no control over this.
When network traffic is high many users’ transactions will be delayed.
You may notice your wallet ID is in a format like this (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx), this makes it almost impossible for a hacker to brute force attack your account. We use UUID for logins as this is the safest option rather than email, which are used everywhere and makes you vulnerable to hacks and spam attacks.