Here are the rules for the monthly challenges as per Julie's Challenge Guidelines thread: "Challenge layouts must contain 75% TLP product (eligible product can be current or retired product from resident designers, or guest designer product that is currently in the TLP store). BYOC challenge layouts must have 90% current BYOC product from the current month's BYOC. Each page counts for one challenge (you cannot use one layout for multiple challenges)." So that covers TLP's monthly challenges...each individual designer has their own rules for their designer challenges, so you could check out the ones you're interested in. I will mention the Gallery guidelines, because of course any LO posted will have to follow these rules at the minimum: GALLERY RULES: Layouts must contain at least 50% TLP products. (Templates count as 15%.) Uploads must be less than 250k. List all credits; no off-site linking allowed.
It depends on the designer. For example, Fiddle-Dee-Dee Designs is a template designer. So of course she expects that you'll integrate kit designers' items into your page for her designer challenge while also making sure you follow the typical Gallery Rules as mentioned above. Sahlin Studio's March designer template challenge rule states to use the template and her products. NBK's designer challenge for March has a "blind scrap" or slow scrap aspect to it and requires you to use 100% of her products. Basically, you have to follow each designer's requirements, which are different for each designer. (I mention both the designer and the month because I don't want someone to come back and say "wait, that's not _____'s requirement" lol.)
It’s awesome to be able to use retired products from resident designers in our monthly challenge pages. If we couldn’t I’m sure some people would forego buying the retiring products.
Since you mentioned me, I'll point out that I don't require you to use TLP products to participate in my challenge. If you choose to participate using non-TLP products, obviously you can't post in the gallery or in my challenge thread. But you still can scrap and post on your blog or in another gallery, and use that link to enter your layout into my Rafflecopter form. As far as retired products go, you can absolutely use them for my monthly challenge. Hope that helps!