Domain expiry timetable is
Expiry - Domain is automatically renewed by Registry for the Registrar (not for the Registrant).
Expiry +45 days. Domain is returned to the Registry and registry refunds the renewal fee to Registrar. But it can still be renewed by the Registrant by paying a Redemption Fee.
Expiry +75 days. Domain goes into Pending Delete (and will definitely drop)
Expiry + 81days. Domain drops.
Pre-Release means the domain is auctioned off sometime before the domain is returned to the Registry (when the Registrar loses control of the domain). This is usually between 7-10 days before day 45. If you win the auction there is still a small chance the original owner will renew the domain and you lose the domain. The domain age is retained. Also, you cut off the ability of all the drop-catching sharks to take a bite at your domain. So Pre-Release is much better than Pending Delete Auctions.
Pending Delete you are bidding on domains which have entered Pending Delete status, which is +75 days after expiry. These domain will drop and it is a free-for-all to try to register it first, microseconds after it has dropped. It's very competitive for desirable domains. Hand-Regging the domain will always lose out to the professional drop-catchers.
So given that scenario, the answers to your questions are..
1. Yes they are both expired domains.
2. Pre Release is better than Pending Delete.
3 Pre Release.
4. It goes to Pre Release first, when it is still under control of the Registrar. When they return the domain to the Registry they lose control of the domain unless the original owner pays the Redemption Fee plus the Renewal Fee to the Registrar to keep the domain. A domain will automatically drop at Expiry +75 days. It will drop on the 6th day after it goes into Pending Delete status (at expiry +75 days).
5. A domain will lose it's PR when it drops at the next PR Update. It will retain it's backlinks. But usually they will erode over time.
This is the case for .com/.net domains
