SAP NW 7.01 SP8 vs SAP NW 7.3

Hello Friends.

I have question in relation to SAP NW versions.

Currently we are on SAP NW 7.01 SP8 , thinking to upgrade SAP NW 7.3. I have following questions :

1. is this SAP NW 7.3 available for all customer or only for ramp up?

2. is it advisable to go from SAP NW 7.01 to SAP NW 7.3? is these two versions are compatible to upgrade from 7.01 to 7.3?

3. what is the difference between SAP NW 7.01 vs SAP NW 7.3 and NW CE 7.2???

4. what are the things we have to make sure when we go for upgrade from SAP NW 7.01 to SAP NW 7.3?

Thanks

Krishna