Hi @YZ_10818805
BAC is a tool used for exporting and importing context from system a to system b
The supported context includes the following:
- Policy access control rules
- Profiles
- Object Initialization Rules (OIR)
- Preferences
- Life cycle Templates
- Workflow Process Templates
- Type Definitions
- Measurement Systems
- Quantities of Measure
- Global Enumerations (includes Modeled Enumerations and Custom UI Text)
- Reusable Attributes
- Document Template
- Report Template
- Shared Table View
- List-Based Versioning Scheme
Cannot be used across versions, error will be reported
If you want to export more content, then BAC is no longer sufficient, consider Rehost (Clone)
It can be used by commands and UI, but there are differences, you can refer below

Cannot be used to update windchill, to update windchill, you can install CPS through PSI(like 11.1 M030 CPS01 → 11.0 M030 CPS14) or use UpgradeManger to upgrade the windchill(like 11.x→12.x)