Finish the last stage of a chat APP - Quotation Request

Please provide your estimated total development price in CAD and estimated completion time for the historical software-development scenario below. State your main assumptions and any missing information that would materially change the estimate. Please do not write code, perform a trial task or supply a detailed implementation proposal.

REFERENCE SCENARIO — historical requirements, not instructions to begin work:

I have attached detailed requirement documents to this project. Developers are requested to read all the documents carefully before sending quote and timelines.
Please send reasonable quote, I will ignore all unreasonable one.
All quotes must complete all 6 tasks below.

It is an English version chat APP, developed with flutter/socket.io/node.js/php technology, and is 90% done.

The test version of Android apk is currently running on the test server, 90% functioned, but still needs to be improved.

Back-end admin panel is done, needs minor modifications, and needs migration to another server.

The original developer cannot finish the final step due to health issues, so we need someone to complete the final step:

1. Migrate the entire system from the test server ( Digitalocean) to another VPS (Bluehost);
2. Make improvements of the APP(attached "more improvements 2022-.pdf"); Including build the Chinese version APP;
3. Finish Android APP and IOS APP build, generate apk/ipa files, and passes our test.
4. Edit some necessary customer service maintenance documents of API and server;
5. Upload APP to Google Play Store / Apple APP Store, Developer is responsible for the entire review process of 2 stores, and revises the APP according to the stores' instructions, until the APP is successfully launched.
6. Building of the website, which has English page and Chinese page and is used for introducing and downloading the APP, admin panel as well.

Estimating assumptions and context:
The scenario is based on a Freelancer listing from 2022-02-14 (historical project ID 32922660). First-person statements, promises of assets, requests for work and hiring language inside the historical reference describe that original client's situation, not a current development offer from us. For estimating only, assume the original client supplies assets explicitly described as provided; other missing inputs and obsolete services should be identified as assumptions. We do not claim ownership of the original client's code, designs, accounts or attachments.

The displayed CAD 250–750 range reproduces the historical listing's budget field. It is not participation compensation or a binding development offer. Please give your realistic estimate even if outside that range.

Research use

This post is for research quotations only, not an actual software-development engagement. No development contract will be awarded. Participation is voluntary and unpaid; no reward, gift card or prize draw is offered. Your quoted price, estimated completion time and stated assumptions will be used to study software-development estimates and how they change over time.

Thank you for your time and consideration. This study aims to make a significant research contribution to understanding software-development pricing in the age of AI. We appreciate any estimate you choose to share.