mint, if I don't answer your questions it's usually because I don't want to be complicit in your dysphoria or the spiraling behaviour surrounding it. I've mentioned several times now that it makes me uncomfortable to be suggesting or advising anything to you, especially since you refuse to seek specialist care for your issues that go beyond skin health. I worry that I'm aiding in making both your skin and psychological issues worse by playing any part in it, no matter if I'm trying to be helpful or not. Especially since you disregard advice to not mess with your skin any further and not to subject a permanently compromised skin barrier with any form of actives. I don't want to be engaged in a perpetual cycle of telling you not to use something, you use it anyway, you have a bad reaction and blame the product then look at another product you shouldn't be using for the same reasons but you'll probably do anyway.
Althea, the 'alternate products otherwise it will stop working' is a common myth with absolutely no foundations. Weather, hormones, geography, health, etc. will influence your skin's needs, eg. you're in skin recovery mode currently but will probably want something else once that's done. The Superdrug serum is great for barrier repair as well as hydration but if you have more severe dehydration (as indicated before the incident) you may need something that focuses more heavily on dehydration or layer more steps of hydration in your routine later on. Just check in how you're going with the Superdrug first. By the sound of it, you're already in a better place and can consider introducing it soon.
Wrt Toleriane Dermo, never leave anything with a surfactant on your face. If you do the cotton pad method I always think it's best to follow up with a thermal spray that you spritz liberally that's tissued off. If you're feeling discomfort post cleansing (tightness) then it's definitely crying out for some hydration but a cleanser (no matter how gentle) isn't the substitute for a hydrating toner or serum.
Buttercup, I'm so glad the Avene cleanser has been working for your DD!
Can't remember who was asking about KP again (Lego?) but Avene also do a 10% urea cream that also includes 1.5% Salycilic and 1% Lactic Acid (not a 100% on the latter two percentages). It is MO based but if that isn't an issue it's probably good for those who have the delightful combo of KP and Bacne. It also comes in a more concentrated version of 30% Urea in a smaller tube specifically for rough elbows, knees, etc. It's the Avene Akerat range and especially on the French sites not crazy money.
NotAMammy, please read through the following:
Basics of an Actives Routine
Where to Start
Anti-Ageing Info sheet
Adult Acne Info Sheet
I can't give any specific product recs as you haven't really been specific in your form about what you are/have been using so can only point to the regular product recs that are repeated over and over on this thread. As a base line that's the Clinque TTDO balm, LRP Toleriane Dermo Cleanser, Eucerin UltraSensitive for combo/oily skin and LRP Anthelios Fluid SPF50 sunscreen. I'll never rec a moisturiser with SPF in it (ineffective) or a physical exfoliant (more likely to harm you than your skin any good long term).
otyt, you'd probably benefit from using an AHA but since you're still in an establishing a good baseline routine phase you'll have to wait a bit but do let us know if it's getting worse/you suspect it's a product reaction.
I got asked for an ID the other day in the supermarket, only after handing it over did I question the reason why as I wasn't buying anything like alcohol or cigarettes. Woman just shrugged and said she was curious 
Yes, Pupsie, SPF definitely on the forefront of my mind. Had a nerve-wracking 24hrs last week as the AB Reddit went a bit postal with news that Japan Post was refusing to ship sunscreens anymore (there have been some issues with customs in the US, Canada, and the UK) but it turned out that policy has been in effect for forever and things are just as they've ever been. On the back of that I stocked up on the SPF I used for summer last year (pricier but it works really well for me and can be used as moisturiser too for me, it's very light and waterproof so happily meets the criteria). I do have a spreadsheet going for all the new releases as they've come out on Ratzilla but haven't checked their ebay/amazon availability and pricing in a while. Also been keeping an eye out for the new releases as they've come up on EPP.
Have also been keeping an eye out for Biore alternatives as I know many of you like it and are worried about the reformulated version. Mostly the Nivea gel comes up, which is cheap and comes in a giant pump but I think the lack of sweat/water resistance and the PA+++ rating make it more suitable for winter than summer. The Shiseido Senka falls into that category for me too, Pupsie, it's not waterproof/resistant.
Dulci, I had read about the red dye (which I feel is a good thing as it will stop people foolishly leaving it on) but figured it may work as a weekly treatment anything to appeal to my laziness, leave it on for maybe 20 mins (maybe 30?) then wash off in the shower. By the sound of it I'd be through an entire bottle after two times though...
Lego, your TO selection sounds sensible. You could also consider in the long term swapping out the Vichy serum with TO Buffet.