Creating apps and games for IOS/Android?

Question

Mobile development

Hello everyone, please help me understand the wilds of mobile development.
I am a web developer with 5 years of experience and until yesterday I had never encountered the development of applications for mobile axes, so please forgive and understand if the questions are too strange :))
So:
1. To create a NATIVE application for IOS / Android, I need ONLY according to ( Swift | Obj-c)/Java?
2. To create native games, is it better to take engines (SpriteKit for iOS / (LibGDX for Android)?
3. If I want to make games quickly / cross-platform, do I need to learn ( C # for Unity + $ for a license) / ( C ++ for Cocos2D)?
4. If I decide to make toys on an engine like Unity/Cocos2D, then I need to know only C#/C++, respectively, without a deep dive into Java/Swift/Obj-c?
5. Do the engines build the finished product immediately under the axles?
6. What is the best thing to take for developing a cross-platform application?
Particularly interesting for cross-platform, as I worked with the Ionic2 (JS) framework and the difference between a native application and a hybrid one is very noticeable.
Thanks in advance to everyone who answers :)

Answer 1

1. To create a NATIVE application for IOS / Android, do I need ONLY the corresponding ( Swift | Obj-c) / Java?

For an application - not a game - usually yes, and Swift and Objective-C are almost the same, but sometimes for the same Android you have to work with C / C ++, as well as with a couple of Assemblers and machine codes :) and sometimes it is advisable to use PhoneGap / XDK / Titanium and write mainly in HTML + CSS + JS, similarly for iOS.

2. Is it better to use engines to create native games (SpriteKit for iOS / (LibGDX for Android)?

Better than what?
The basis of the game, unlike the application, is the "engine", either write it yourself or take it, there is no third way.
Игры - отдельная область, но сколько-то взаимодействия с API ОС все равно понадобится, также использовать сборщики вроде Gradle, и общие навыки отладки и т.п., а последние три пункта входят в Java/Swift/Obj-C.
Некоторые "билдят", некоторые просто библиотеки, во втором случае явно IDE и сборщики те же что и для приложений.
Маркетолога, чтобы сперва убедился действительно ли стоит делать кроссплатформенным.