Question Related to LLM specification & Costing

My team is working on M365 Copilot using various approaches, including Message Extensions, API Endpoints, Graph Connectors, and Copilot Studio. I have a few questions regarding the AI aspects of the system:

1. Which large language model (LLM) is being used in M365 Copilot? Specifically, what is its version, token size, costinf etc.?
2. Is it possible to modify the LLM model or adjust parameters like temperature?
3. How can I access and review the conversation history?

I haven't been able to find relevant documentation addressing these questions.