Phase A: Architecture Vision is the first phase of the Architecture Development Method (ADM) cycle, which is the core of the TOGAF standard. The main purpose of this phase is to define the scope and approach of the architecture development, and to create the Architecture Vision, which is a high-level description of the desired outcomes and benefits of the proposed architecture. To achieve this purpose, this phase focuses on defining the problem to be solved, identifying the stakeholders, their concerns, and requirements, and establishing the business goals and drivers that motivate the architecture work. This phase also involves obtaining the approval and commitment of the sponsors and other key stakeholders, and initiating the Architecture Governance process.
The TOGAF Standard, Version 9.2, Part II: Architecture Development Method (ADM), Chapter 5:
Introduction to the ADM : The TOGAF Standard, Version 9.2, Part II: Architecture Development Method (ADM), Chapter 18: Phase A: Architecture Vision : The TOGAF Standard, Version 9.2, Part II: Architecture Development Method (ADM), Chapter 18.3: Inputs : The TOGAF Standard, Version 9.2, Part II: Architecture Development Method (ADM), Chapter 18.4: Steps

Gap Analysis in TOGAF is a technique used to compare the baseline architecture (current state) with the target architecture (future desired state). The output is a set of gaps, representing what is missing or what must change to move from baseline to target. These gaps help validate that the target architecture is adequate:
by identifying what is not addressed, architects can ensure that all required functionality, constraints, and transformation paths are captured. In effect, Gap Analysis validates the architecture by exposing omissions, inconsistencies, or unmet requirements between what is and what should be. It is not primarily about defining service levels, nonfunctional requirements, or quality metrics (though it helps inform those). Rather, its main role is in validating and guiding closure of architectural gaps.

An Architecture Contract is a deliverable that specifies the responsibilities and obligations of the parties involved in the implementation and governance of an architecture. It ensures a system of continuous monitoring to check integrity changes decision-making and audit of all architecture-related activities.
Reference: The TOGAF Standard | The Open Group Website, Section 3.3.4 Architecture Contracts.

The TOGAF standard covers the development of four architecture domains: Business, Data, Technology and Application. These domains represent different aspects of an enterprise's architecture and provide a consistent way of describing, analyzing, and designing them. Reference: The TOGAF Standard | The Open Group Website, Section 2.2 Architecture Development Method (ADM).