Who designs parts of applications, like screen interfaces, middleware and programming infrastructure, that complies with head applications developer's design principles and falls into line with their SDLC?

Applications architect

Explanation:

In a team of computer programmers that specializes in application development, the lead is called the Applications Architect.

The Application Architect has the following duties:

Employs modeling to discover problems, reduce cost, test multiple outcomes and so on, Understands the global marketplace, technology users, competitive environment, IT strategies, and key technologies that make the foundation for development, Manages all application-specific tasks, Provides technical guidelines for proper development and maintenance, Full understanding of the whole system process flow.

The role of the applications architect cannot be underestimated, hence the need for an experienced and versatile hire.