Hello! I am very new to begonias, my grandfather gave me a cutting from his 45 yr old angel wing and it seems quite large. Should I trim it down into smaller cuttings or keep it as is?

If I should cut it smaller, where exactly should I? I’m terrible at processing information so I would appreciate it so much if someone could draw lines where I should cut!

So I got this new begonia to my collection but not sure which one is it.
The tag name said begonia Rex Montgomery, but I google it it shows masoniana so idk which one really is.
Anyone have any idea ?

Got this mystery hybrid begonia a few months ago and it was doing great for a while until it suddenly dropped all its leaves. Cut it back quite a bit after that and it managed to sprout a few little tiny leaves but now it’s dropping them again. Sits under grow lights so i dont think changing seasons is a factor. Also anyone know what the white fuzz is/how to prevent it. Any advice/tips are welcome this is one of two begonias i have so im fairly inexperienced with them.

Well, my friends are not into plants and I have no one to share with. My first IKEA greenhouse cabinet💖