Web & Mobile app development (Chat + task assignments)

Hi
I am building a chat application (preferably matrix based) that has the added features of sending new category of messages such as tasks and appointments (with acknowledgements, dates and deadlines). This app will also offer cross-platform messaging. I am looking for a full stack developer who will help me figure out the right technology stack, development roadmap for back-end and front end as sprint planning etc. The product will be mainly mobile based but will also have web-features.
Key deliverables will involve
1. Technology Roadmap
2. Define Engineering requirements (from already developed user stories and requirements)
3. Back-end development
4. Front-end development (limited to MVP stage)
5. integrations (for other chat apps)
6. Hosting and operations plan
7. Payments and billing on time and feature basis

This is an academic project so looking for someone from India with previous experience in managing and executing software development projects. Turn-key services quotation are welcome with a maximum budget of INR 100,000-150,000. This can be negotiated based on the expertise and level of services that the developer can provide.

Payment will be made milestone based.
NDA and non-competing agreements need to be signed.

For further inquiries, feel free to message/chat.

Regards
Jameel