React-Bootstrap v2 and Bootstrap CSS major-version pairing: what is actually supported?

React-Bootstrap does not ship Bootstrap CSS, so the application must include a compatible stylesheet separately. I am planning a migration from React-Bootstrap v1 (Bootstrap 4) to v2 (Bootstrap 5) and need to pin down the exact compatibility contract before touching component code.

The uncertainty is around the boundaries of that contract. The v2 line is documented as targeting Bootstrap 5, but it is unclear whether compatibility is tracked per major version only, or whether specific Bootstrap 5 minor releases are required for certain components. There is also the open question of how the project handles newer Bootstrap majors: whether support lands in the mainline package or in a parallel release line, which affects upgrade timing.

A second constraint is that Bootstrap 5 renamed data attributes and dropped jQuery, so markup and prop expectations from v1 do not carry over unchanged.

1. Where is the authoritative declaration of the supported Bootstrap version for a given React-Bootstrap release — peerDependencies, docs, or both?
2. Is mixing React-Bootstrap v2 with Bootstrap 4 CSS ever viable for a gradual migration, or is a hard cutover required?
3. Which components (Modal, Tooltip, Dropdown) are most sensitive to CSS/attribute mismatches during verification?