Answer 1

It is possible in a few ways. For one of it Microsoft Xamarin you can read here:

https://dotnet.microsoft.com/en-us/apps/xamarin/mobile-apps

More information about another possibilities you will also find out in web.

Answer 2

I'd rather go for .NET MAUI instead of Xamarin

Answer 3

Of course, but rather after .NET MAUI will be ready:

https://docs.microsoft.com/en-us/dotnet/maui/what-is-maui

Answer 4

Xamarin will be replaced. In fact the only reason it's still in it's lifecycle is because MAUI got delayed. It should've ended last year.

Wouldn't make much sense to start new Xamarin projects. Especially as a beginner.