I think it's only beneficial if you are using an oil-based cleanser for your first cleanse. Otherwise, you're just stripping your skin of its natural oils if you use a foaming cleanser twice :/

not a must, but definitely good to have. i do think the first cleanser will break down any makeup, remove dirt and excess oils from the day and clean your skin better than if you use only one.

not necessary at all! :) personally I just use micellar water and it works fine for me. but I've been learning here too, seems like most people do use two types of cleansers.

It's not necessary, if your skin doesn't need it! Personally, I found a lot of my acne issues clear up when I did introduce double cleansing into my skincare routine. Like below, I think it's about cleaning your face properly so that you don't have gunk on your face when you do your skincare routine :)

I don't think it's necessary. Cleansing thoroughly without disrupting your skin barrier is what matters most. You can reset your pH balance with a toner. If you can find a good foam cleanser to get everything off and not dry out your skin, I don't think you need two steps!

Not a must in the morning! I think the point of double cleansing is to make sure you are properly cleansing everything off your skin – dust, gunk, make-up, spf and all of that which you accumulate throughout the day. You can use makeup remover or micellar water for a first cleanser, but my favorite is using a cleansing oil because oil attracts oil and it helps get everything off your face. Then I go in with a gentle 2nd cleanser (usually foaming) to wash everything off my face and prep for my skincare routine.

IMO it's necessary, especially at night if you use make up and SPF. I saw huge improvements to my skin after double cleansing and I'll continue to do it!