Help with features to look for in platforms when starting e-commerce

I have taken on a project to help some friends, and there are points where I am stuck. First of all, there are some cash constraints; I will be helping for a nominal fee anyway, as they just want to realize a nice idea.
1- First of all, which infrastructure should I use?
Wordpress-Opencart-Magento etc., or ready-made systems like Ideasoft-Tsoft?
2- How can I handle email and SMS notifications to the customer when a product is purchased, when membership approval is required, or during campaigns?
3- When a user registers and logs in to the site and buys a product, I want to send a confirmation email and SMS to the customer. Additionally, there needs to be a feature on the site where suppliers can instantly track the customers who bought products from them. Because the customer buying the product from the site will pay us, then go to the supplier to pick it up. How can this be tracked by the suppliers, or how can supplier integrations be used? We are particularly stuck in this area because the supplier needs to know who bought from them and mark this data as “sold” or “delivered” after providing the product/service, to protect against potential issues in the future…
4- Although not mandatory, a live chat feature is requested for the site. How can I use this in the infrastructure you recommend?
I genuinely need your help and suggestions. Thanks in advance.

Let me write down my thoughts.
1 - Definitely do not use a ready-made system. Use systems that you can customize for yourself. I think OpenCart and Magento will already be sufficient for the job you are going to do.
2- You can handle the email notification feature with **mailchimp **. With the free membership, you can send up to 12,000 emails per month. You can define a mailing list of 2,000 people.
3- I cannot say anything. It will depend on the infrastructure you will set up. Other friends will already express their opinions.
4- You can use zopim for live chat. It will do the job more than enough. The price should be 14 dollars per month. You can use a 15-day trial version.

Thanks. For now, the only thing I’m stuck on is that suppliers need to be given a separate membership by the site admin so that they can track only the sales of their own products, meaning who bought them. I would like to get paid or free help from those who have an idea about this or who can edit code or write a plugin using any infrastructure. I would be very happy if friends with ideas could reach out here or share their suggestions.