1) if i use GPIO_Mode = GPIO_Mode_AF; then how to configure the GPIO_OType?
2)Generally what are the cases that PUSH_PULL will be used?
Can any one Please help out.
Note that this has nothing to do with Keil or ARM.
community.arm.com/.../158950
These are specific features of the ST product - so you need to go to ST for help.
ST have lots of resources, examples, etc to get you started with their STM32 products:
https://community.arm.com/developer/tools-software/tools/f/keil-forum/35918/not-able-to-see-variables-in-memory-window/109675#109675
The AF sub-system will select an input mode for USART1_RX
Just set, or leave, the PUSH_PULL setting for the GPIO Initialization structure.