Multiple prices for sizes of the same product

You need to create a "size" characteristic via the menu Products->Characteristics. Then, when you edit the product, add that characteristic in the characteristics listing on the right and save your product. Then, you can click on the "manage variants" button of that zone to see the listing of variants of the product. You can edit each variant and add a different price for each.

For our documentation, you can go there : www.hikashop.com/en/support/documentation.html
Here, you will find all our documentation articles: www.hikashop.com/en/support/documentatio...d-documentation.html
And there, you will find an explanation on the characteristics: www.hikashop.com/support/documentation/i...html#characteristics
I see that you set two unit prices for your product. That is not possible. You should set only one unit price per variant. You can have a look at our demo website:
www.demo.hikashop.com/index.php?option=c...ow&Itemid=57&lang=en
There, the price was added for each variant of the product. The price is automatically updated based on the characteristic selected in the dropdown.

1. You can change the display format of your currencies via the menu System->Currencies

2. You can edit your characteristic values to include the price in it. Then, you can hide the normal price displayed with some CSS in your template.

The "per unit" can be changed by editing the translations in the configuration under the tab languages.

You can create several characteristics, with the same name if you need that, and add the relevant ones to your products.