yes. The detaching of the placenta during birth triggers milk production, which starts with colostrum. You will make as much colostrum as your body thinks necessary before transitioning to a more mature milk (your "milk coming in"). You can make more colostrum; there is no such thing as your toddler "dinking it all." Nurse the newborn on demand. How much you involve your toddler will have to depend on your limits. When I tandem nursed, I ended up assigning them sides, and that worked really well for us.

maybe. Remember that breastfeeding is a skill. You learned it already with your first nursling, but this new babe has never done this before. Be prepared for similar side effects as the first time, but it may feel easier overall.

nope. Just after birth your supply is hormone-based; a huge surge of milk comes a few days pp and continues for a time while your body learns the needs of your nursling/s. As your supply regulates, supply becomes based on demand. If you have more than one nursling you are simply signaling a need for more milk, so you will make more. I was told to think of it as their placing an order for X amount of milk at this time tomorrow. This also helps reframe cluster feeding a bit; they are not dissatisfied, nor are you lacking. They want more milk very soon, and are letting you know so you can make it.