Design responsive layouts across artboards

We must hand off responsive layouts to product by Friday. Arrange artboards for desktop, tablet, and mobile with consistent naming, show how elements reflow with simple notes on constraints, include a link to the design token list, and run a quick pass to ensure type scales and grid alignments match across artboards before you send to Elena in product for review.

Before this goes to stakeholders, make the responsive behavior obvious: add an overlay on each artboard that highlights which elements are fixed, which scale, and which reposition; surface the breakpoint widths and lead type sizes up front; and flag any components that depend on scripting or non-standard fonts that could change layout in implementation.

The product manager just pushed back: on mobile the primary CTA floats, while design shows it fixed to the bottom. Elena wants rationale tied to analytics and dev constraints, and marketing wants it always visible. I'm not sure which decision balances conversion and accessibility and I can't show live metrics for this component. Given we have three days before the sprint, what's the likeliest trade-off and the best recommendation I can defend to get consensus?

Over multiple releases we waste time tweaking breakpoints and constraints after engineering builds. Breakpoint debates bleed into QA and push timelines. I want a durable habit that reduces late changes. Which parts of our spec or handoff should change, what small prototype or example convinces engineers faster, and what rule about when a breakpoint can be altered after sign-off would stop endless reruns?