I’m going to resist saying too much about a breeder of mixed breeds being registered, registered with who though? It won’t be the Kennel Club so any other registration you receive is just a bit of paper.
Apart from that -
If the pup is raw fed just now you should continue this. The breeder should supply you with a minimum of a weeks supply and a feeding schedule. Depending on age, pups need to eat 4 times a day and will play, poop and sleep in between feeds.
Have you got a freezer for the dog food? Raw feeding can take up a lot of space and needs to be properly balanced for each life stage. If the breeder doesn’t give you a detailed plan visit the Raw Fed and Nerdy Facebook page.
Pups will sleep. A Lot. Overstimulation will be counter productive, think of it like being a new born baby.
Crate training is a good idea, especially as you admit you are not experienced with pups so there may be dangers you haven’t thought of that the pup could get into during unsupervised time. Never ever leave the collar on when he is in the crate.
If you look on YouTube for Susan Garrett’s Crate games you will see a system to acclimatise the pup to the crate but the breeder should have introduced the pups to crates before they leave home. Crate Games is an excellent and fun way to bond and train the puppy. Well worth doing.
Re socialization - that is going to be a complete nightmare. Ideally you would be carrying the pup to places like supermarkets so they get lots of sights and sounds, speak to people and see people with walking aids, wheel chairs, trolleys etc.
As you can’t do that the best you can do for now is play sounds like fireworks, trains, lorries etc. There are loads of puppy socialisation playlists you can play. Start playing them quietly while stroking the pup and talking calmly, gradually building up the volume.
Also dropping things is a good exercise so the pup is not startled by loud sounds. Start with something like a tea towel and drop it in sight of the pup (but not near) and then give the pup a reward and lots of praise. Build up the closeness to the pup as well as the noise of the item so eventually you can drop a big pot or something and then pup is not spooked but expects a reward and praise.
Make sure the breeder sends you photos of the brushes and scissors you will need to groom the pup. Start by running the brush over him then reward with a treat or a game. Increasing the time you spend brushing day by day making sure he is used to you touching him all over, lift his feet, tail etc. If you don’t groom him he will become painfully matted.
If he is less than 12 weeks old he won’t need vaccinations yet, he will have immunity from his mother until that age. If you do decide to vaccinate him at 12 weeks do not allow him to have Lepto4 which is a combination of 4 injections in one. There are many cases of pups and adults having boosters who have seizures and fatal responses within a few hours of Lepto 4. Call round the vets and find one who will use individual vaccines.
He may not be used to wearing a collar or lead yet so every day put the collar on then. Play a fun game or put it on before he eats so he is distracted by something else. Puppy leads are nice and light and it’s good to have him get used to being attached to something so clip it on, have fun together for a minute or so then take it off. Do this several times a day and increase the time each day. Let him trail it behind him, walk with it in your hand, drop it etc, get him used to all options.
I would totally recommend getting a clicker and using it to help bond and train the pup. Especially during lock down you will be able to train so many little exercises and tricks at home using the clicker. Google Dog Games or positive clicker training. You will get loads of fun ideas on there and clicker training is really easy but very rewarding.
When you can finally go walks remember the rule of exercise - 5 min off lead exercise per month of life per day. It’s not a lot. Pups given too much free running will damage their bones, right now he will have big gaps between the bones right now which grow until the growth plates close. It’s really important not to allow the pup to run wild all day long even if they want to. This is where tiring him through mental stimulation and clicker games will be your best way forward.
I hope you enjoy the puppy and you know you need to post pics!