1. You can show products on a page via Products element, but in such page default WC widgets do not work and pagination cannot be enabled.
“Add to cart” button can be enabled for grid of products via Theme Options > WooComerce (Shop) > Products style > Product Content Elements.
2. You can enable Single Product Builder via Theme Options, it allows to create the content of single product page from scratch depends on your needs, and use Multiple Templates.
Size Guide settings you can find in Theme Options also, use search – https://prnt.sc/ucemne
3. Only products can be added to the cart.
Regards