Apex is a custom ROM built from I9000 source for I896/I897 captivate. Three stable builds of Apex are available based on different base:

1. Apex 9.x - Recommended

Based on 2.3.4 XXJVR 

2. Apex 8.x - Final, won't get any updatesBased on 2.3.4 XXJVQ 

3. Apex 7.x
Based on 2.3.4 XXJVP - Final, won't get any updates

4. Apex 6.6
Based on 2.3.3 XXJVO - Final, won't get any updates