Change Password Functionality - SAPUI5

We have custom logon screen and having "Change Password" functionality, how can we achieve that in SAPUI5 ?

From UI5 application change password service needs to be called, which will eventually change the password.

Scenario 1: What happens when SAP User Account is expired (service can not be invoked)

Scenario 2: What happens when SAP User Account is locked (service can not be invoked)

Scenario 3: In SAP password can be changed only once per day ?

Scenario 4: Before logging in if user want to change the password, how to invoke the service as the credential may not be known to invoke the service ?