Android user has a new iPhone SE...

[beastykato]

...and he has some questions. Now admittedly I'm a little disappointed with this phone in regards to battery life and some features. However, the phone performs great and it does feel premium in the hand. I think I can manage with the battery life if I get a partial charge in during the day. I don't think I'd have paid $399 for it, but with all the $184 and $200 range sales on it seems like a good deal.

There are some features here I'm really disappointed in not having, but I'm asking because it may just be me not knowing how to access/use them on iOS.

1. Youtube. On Android I can watch Youtube videos in the corner of my screen and continue to browse the web and access other applications. When I close the youtube app on this iPhone it actually closes and stops playing the video. Is this not possible on iOS?
2. Casting. So, I have multiple FireTV's in my home. I fear this is why I partly stayed away from Apple in the past, but I can't seem to cast to the FireTV and I'm not buying AppleTV's just to buy into their ecosystem to cast. I did find an airplay app free on the Amazon app store, but it has ads and is very cumbersome with poor video quality. On Android, you just hit cast and boom your YouTube video was up on your TV. Is there an app than can do this function for me on iOS? If it costs money I think that's kinda BS for a feature that should come with it, but I'll contemplate spending more money if I keep this phone long-term.
3. Tiny Phone Screen. So, the small size of this phone is one of it's features and one reason I like it. However, I like to play games on larger screens, typically I would cast to do this or use my larger android tablet. I saw that Apple sells an HDMI and power dongle for $50 (... really is there a decently priced one? that's ridiculous.) When you do this what is the output resolution and is it adjustable? Will it fill a full size TV screen?

I think that's all I can think of at the moment. All in all, the phone itself is pretty nice and I like iOS. I definitely haven't converted because I'm finding a lot of little closed ecosystem nitpickery things, but overall it's been a good experience so far.