giftcards. com is owned and operated by Blackhawk Network, I don't think anyone earns credit card points nor cb on cc.
However, I know that My Points has a 1 point per dollar from them and that was bumped up to 2 points per dollar during one of their sales last year. So if you bought the max of $750, you got 1,500 which is equal to $10 towards a Virtual Visa plus the 1% general reward amount from the credit card. Every little bit helps!
Will a Universal gift card work for Annual Passes online?
No, it doesn't appear that you can use them to purchase Annual Passes online.
One thing about Universal is that their online system isn't set up to take multiple forms of payment for one transaction. If I recall correctly (and please don't take this as gospel since I called about this almost two years ago), their phone system can't either. The physical parks, restaurants, etc. can. So even if they can take a gift card over the phone to buy an annual pass, you would need a gift card large enough to cover the entire cost of the pass. And there is no website to combine gift card balances.
In addition, when I wanted to use a gift card to upgrade my annual pass, it couldn't be done at the ticket office at the hotel. We needed to go directly to Guest Services. We stopped at the one in City Walk on our arrival day and there was no line, but if you are trying to make early entry on your first day, that might be an issue.
That being said, you can often purchase discounted Universal tickets and then upgrade them to APs later. For instance, earlier this month, my friend bought a 2-park, 3 day ticket for about $30 off Universal's online price. Then she was able to upgrade it to a seasonal AP at no cost. If you chose to go this path, it would be best to keep your ticket money as a virtual Visa and buy through a reseller.