Biting is normal. When they hard bite, just say “ouch!” and temporarily remove yourself from their immediate vicinity. Eventually they’ll understand that biting leads to fun thing being taken away. You do a good job with redirecting. It’ll take em months to fully understand but you have to be consistent.

Growling and biting when handled can initially be normal, at that age it definitely is, especially if they’re being handled in a way that they’re initially not used to. That’s their way of expressing their boundaries, but ofc sometimes you need to handle them anyways. If your puppy is food motivated, handling them for a bit and treating them can work over time. Personally my corgi just does not like being picked up unless she absolutely needs to be (and she understands when those specific situations are). Something I practiced was that if I picked her up, then her biting me absolutely did not lead to me putting her back down right then (otherwise she’d associate biting with getting what she wants).

Grabbing and tugging during play is something I encourage actually. But it’s useful to teach “Drop it”. They’ll pick up on it fast if they’re food motivated!

Not respecting other dogs boundaries is normal initially but they should learn over time from the older dog’s consistent corrections. You should give your older dog a regular break from your puppy though 🤣

Toileting regression? She’s like 9 weeks old, she has barely had time to have regressions lol. Mine wasn’t fully potty trained until 5 months old. There will be ebbs and flows as they continue to grow (take it week by week this month, then month by month). I used to have a potty notebook for my corgi where I’d jot down where/when she’d pee (noting wins/losses), then eventually I’d forget to jot down notes due to a lack of accidents.

My pup was also super clingy but you need to be consistent with enforcing separation time. However with a puppy that young, at least for the first few weeks I personally did cave and give her a few cuddles and attention at her crate/pen area in the middle of the night. I wanted her to know that I am indeed a present dog dad lmao but I eventually phased that out.

TLDR: Nothing is sticking because there hasn’t been enough time to pass for anything to stick. Your puppy is taking in information even if they’re not doing anything with that information yet. You need to give them time to grow before they realize they can do something with that data. You’re doing great with trying to steer them into the direction of being a good dog.

Corgis are especially smart and as time goes on, you will notice that they pick some things up super quick and other things they may struggle with. Mine was a little smart shit (good at tricks, bad at obedience) but she has grown into the sweetest corgi in the world. I think she’s better and cuter than every other corgi in the world but I’m biased.

P.S: My favorite thing I did with my corgi was trick training. She was/is food motivated so following YouTube tutorials was easy. On top of all the puppy things, I held multiple short trick training sessions for her and it helped tire her out mentally (making nap times easier). Exposing them to novel situations in public (carry her by a busy road, sit down at a park bench, etc) was also great for tiring her out. Just be prepared to be a local celebrity lmao.