No, not yet. Obsidian is only available for Windows, macOS, and Linux right now.
Mobile apps are in our long term plan, but they will definitely take a while.
Fortunately, Obsidian data is just plain text Markdown files, so there are plenty of great tools around. Please see here for a comprehensive list.
Not yet, sorry. A Typora-like WYSIWYG editor is on our long term plan, but it will take a while.
Please post them on our forum. Thanks for taking the time to help improve Obsidian!
If you already have a folder of Markdown files, that would be perfect and nothing needs to be done.
Many apps can now export to Markdown files, and that's a good starting point and should probably work out of the box.