Adding variants without choosing

I want to add variants. For example: I have to make a gallery for a painter. There is a lot of paints and 3-4 sizes. Every paint have an only size (it's not possible to have this paint in another size). But I want to be able to add the relevant size to the paint with a variant. But I want to disable the possibility from the user to change the size. Is is possible?

Also, is there a possibility to write instead of price (numbers) something like "contact us"?
And the last one: I want to add "click on picture to enlarge" above the thumbnails. Is that possible?

Thank you!

Hello,

1. If you want to use the variants like this it will be no use, but you can maybe use customfields.

2. Yes there is, you can use the catalog mode then you'll have a "contact us link". BUT, you have to know that in catalog mode your customer can't add items to their cart so all of your "add to cart button" will disappear.

3. You'll have to modify the code of your product view (through the show_block_img file).

Hope this will help you.

I think you are right, I need custom fields. I understand that it's only for commercial version. Which of them? I only need to display on frontend more information about the product. just like here:
www.eranalgor.com/gallery/eran-algor7.aspx