I have created a few receiving addresses using iota wallet. Is it safe to send iota to those addresses, or do I have to wait until addresses are confirmed?
Addresses are derived deterministically from the seed.
In order to receive iotas your address doesn't have to be in "confirmed" state. In fact, You could even decide to not attach your receiving address at all, and you would still be able to receive iotas to that address, and spend from it.
It's encouraged to reattach receiving addresses in the current wallet so you can keep track of your addresses, and by attaching you help confirm other transactions.