I will develop dynamic web apps with mern stack

Both. Adding features to a working codebase is fine. If the existing code is in bad shape, I'll tell you what needs fixing first and quote it separately rather than building on top of a problem.

One distinct screen with its own route and its own data. A dashboard with four tabs is one page. A landing page plus a login plus a dashboard is three. Message me with what you need and I'll tell you the count before you order, so there's nothing to argue about later.

You do, entirely, on delivery. You get the full repository, no dependency on me to run, deploy, or change it.

Yes. I configure and deploy to your accounts (Vercel, Railway, MongoDB Atlas, or your preference), but the service costs are yours. Most small apps run on free tiers to start, and I'll tell you upfront if yours won't.

Yes, as any modern engineer does. Every line that ships is reviewed and understood by me. You're hiring my judgment; the tooling is how I work faster.

If it's a defect in what I built, I fix it, that's not a revision, it's my responsibility. New requirements are separate work and I'll quote them.