That's a nice peach picture you created, but to answer your question, no, you do not have to do any assignment before your proposal is accepted. That does not mean you cannot do it before you have a contract, but DO NOT send your work to the client until you're hired. If you send work without a contract, the client might not pay you and you will get no help from Upwork in getting paid.
Welcome to Upwork Ayesha!
No, you should never start working without an active contract, which would show in your "My Jobs" tab. You can find more details here. If a client accepts your proposal and responds to it, the proposal will be listed in the "Active Candidacies" section of the Job Applications page. You then need to discuss the project scope, requirements and contract terms with the client. If you agree to work together, the client needs to send you an offer and you need to accept it, in order to have an active contract on Upwork. Make sure not to start working unless the contract is covered by the appropriate Upwork Protection Program and only accept to get paid through the platform.
You can find valuable information in the Getting Started as a Freelancer section of the Help Center and by reading our Freelancer Guide. I also suggest watching our educational videos and reading the best practice advice shared by other users:
I just recently became a freelancer on UpWork, and i recieved an Invitation to Interview, i just wanted to know a few things as this is my first job and i want to make sure i do everything right.
1) How can i make sure that that the job is legit?
2) Once i accept what is the procedure?
3) How does the payment system work?
4) is there any useful tips that you all have for me that will help me as i start this journey?
5) Can the client not pay me for any reason?
I would greatly appreciate the support and advice even if it isnt related to my questions.
Thank you kindly
I moved your comment to this thread so you can check the resources I shared with the OP. You can find answers to the questions you posted in these resources, and detailed advice and tips on other aspects of working on Upwork as a freelancer.
Let us know if you have any questions.