It shouldn't affect fading. It has the potential to be harmful to the fabric though, be sure to wash it out when they become soft again.
I don't see any difference in description between the pair on BiG. Can anyone confirm this?
Newer lots are going to fit a teeny bit smaller, not so much that it'll make huge fit differences tho. With the lots, they'll change the samples a bit as a model pair for others to be produced. It usually has to do with minor measurement differences tho, everything else should be the same.
The two are listed under different items, one a lot 12, the other a lot 13. The lot 12 has a link to the lot 13 in the description.