To naturally remove limescale from a chrome shower head without damaging the shower head you can take a plastic Ziploc bag or other plastic bag and add some white vinegar to the bag and some hot water mixed in with the white vinegar inside the bag.
Then tie the bag with the vinegar and hot water to the shower head and let it sit for 2 hours or longer and then remove the plastic bag from the shower head and let the shower run with hot water for a few minutes.
If you see any other shower head spray holes clogged you should put the bag back on with some more fresh water and vinegar and let it sit for another few hours or overnight.
Then run the shower again to clear the passages.
Apple Cider Vinegar or even some CLR cleaner will also work to clean the limescale from the shower head by using a plastic bag again or you can remove the shower head and let it soak in a bowl of limescale or vinegar to clean it.
But putting a bag of vinegar or the CLR on the shower head will work just fine without the need to remove the shower head.