You can select multiple files in the preview select dialog.

Your paranoid friend must trust the site and the mod author or he can't play with mods hosted exclusivly on our site.
You have to buy the game on Steam to download from our site, because we're not going to change that. For reasons look at the various discussions in this group or on reddit.

Is it correct that this is no longer a problem?

You need a copy you got via Stream Family Sharing or by buying the the game on Steam, so you need to be able to lauch the game from Steam when you're logging in with the same account you want to use for the website. This is not the case for your account since rebirth would appear in the recently played section on your steam profile page.

See https://gtm.steamproxy.vip/groups/moddingofisaac/discussions/4/364040961439454971/

This is because of how the shop is generated, only 12% of the icons in the shop are the "rare" afterbirth icons. Together with the fact that they are 186 afterbirth icons (the ones that cost 30 coins in the shop) and only 119 special icons (the name is from the time when the afterbirth icons did not exist and they were the icons to buy in the shop), makes it quite hard (impossible) to obtain all icons. Additionally there are 5 reclaimable and 1 unobtainable icon which show up under stuff i found on the profile page.

I will not change the algorithm because i did this once, by using only one pool containing all icon and noodle reverted it and I respect this decision.

Making sure that one buyable icon is the shop will not happen because the icons in the shop are randomly generated when they are needed and so this would cause an other buyable icon to appear after one bought a icon from the shop.

The reroll function is the best solution and has been requested before (I think), but I have no idea how to implement such a function.

This is not possible. You must own Rebirth to download mods.

You were propably trying to install my mod manager, but as the description clearly says, its currently broken, because I changed how login works on the website. I will fix it when I finished the api for the website.

You have a shared copy when someone owning rebirth gives you access to his steam libary using steam familiy sharing. You dont seem to have such version as rebirth would appear in your recently played history.
We dont grant full member accounts to persons not owning rebirth.

You may have logged in with a wrong account. (The account used to write that comment has no access to Rebirth on Steam)