Internal optimization of the site

You need to make an internal optimization of the site:
You are required to:
Creating optimal internal linking
- selection of the semantic core
- Optimization of pages
- Heading optimization
- Creating a site map, Robots.txt
- meta-tag writing
Creating “meaningful” URL pages
Optimization of key queries
- Internal code optimization
Internal optimization of design
- Image optimization
- 404 error
And so on.

We have questions for you:
The site will be a bulletin board for the whole of Russia, is internal optimization necessary for this site? Or something specific? Please write what and how much will it cost?
- Internal optimization of the site you will do in parallel with 2 programmers who create the site and writes cms? Or do you do it after you create a website?
How long will it take to optimize the website internally?
How much will this complex of works cost together? We can describe it separately together.

Thank you in advance for your reply. Eugene.