As to your questions.
Currently, there is no TypeScript definition for the Everlive JS SDK. You can vote for this feature request or share your opinion here
Regarding the Windows Phone support, we plan to directly introduce Windows Universal (8.1) support skipping the Windows Phone (8.0) support, but at the moment I am not able to provide any specific time frame in which this will happen.
Out of curiosity, what is your scenario which requires Windows Phone support rather than Windows Universal?
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items