Unity5 Infinite progressive 2D level; WIP

In my current #indiegame development journey, i was trying to implement a infinite 2D side scrolling game. My questions are
how many sprites unity can handle ?
Is there difference between texture atlas and individual tile for 2D also ?
How to import and load Tiled map for the game ?
How to render a 3D trail render over a 2D tile set ?
and so on..
After answering all the questions now i had implemented a optimized(debatable) to load more than 650 sprites and over 4030 objects totally.
So here is my #screenshotsaturday for this week. Which bg tile set you prefer?

 I am looking for other free bg tileable tiles options too..