My first micowave, back in early 70's was just a large space. I was told that something hidden in its revolved. Wonderful, could place large, oblong casserole dishes, etc in there. Lasted the family usage for a good twenty years. Then one of the children slammed the door shut so hard and with something it he way, it shattered the glass in the door. Manufacturers were surprised that it had still be working, and could not supply a replacement door. So, purchased a new one, but now ALL had those revolving turntables. I was told that the public liked to see the food moving round and did not trust it was safe if they could not see that.
Put up with those until last year, had my kitchen done and found that the big boxes without turntables are back in fashion. Delighted as it is so very easy to keep really clean, even with the occasional exploding food!!
Stale, spilt milk has a disgusting and lingering smell. In my first year in my flat I knew I needed to replace the existing carpets but was not sure whether to have it all re-carpeted or have laminate as I had in my previous house . Decision easily made when I knocked over a lovely banana milkshake I had just made. Despite mopping the carpet immediately, and then steam cleaning the area, the smell lasted well over a week, although every day, I steam cleaned it and used a carpet shampooer on it. Laminate for me.
ANyway, back to that microwave, yes lemon is good as is baking soda. Indeed, keep a small amount of soda in a dish in the microwave when it is not being used for the next couple of weeks will also help to prevent that horrible milk smell.