[garbear]

the left/right sticks doesn't work in gaming. I tried several games with FBA core, there is no any response for the left/righ stick, but when exiting gaming, the left/right stick works in the Kodi.

This is an input error, which makes sense as I overhauled the entire input system over the last few months. Can you help me reproduce? Which games use analog sticks?

I just created a share from PC for the ROMS I have, Kodi can see the share and ROMS, but when I tried to play, it said only support local drive, not network share. Is this expected? Why is there such limitation?

In our game add-ons wiki page (https://kodi.wiki/view/Game_add-ons#Libretro_cores), you can see a column for "Supports VFS". VFS stands for Virtual File System. This means that the ROM doesn't have to be sitting on the HDD, but can be located in a .zip file, a Windows share, or any of the other million protocols Kodi supports.

The reason why every core doesn't support this is because adding VFS support is an incredibly labor-intensive process. The emulator's source code has to be modified, usually against assumptions baked into the code since day 1. This can require architectural changes, which are never easy, quick or safe. And what's worse, this process has to be repeated for each. and. every. core. I spent several hours working on input for every core, and this took almost three months. VFS support for every core would be worse.

libretro maintains our cores, so if you need VFS support, I recommend you start by asking them.

The game screen only takes up the middle part of the screen, is there any way to stretch the screen, to make it full screen, like the MAME4droid? 

Try settings -> View Mode in the in-game OSD.