so example even if maybe I can complete all the quests in episode 2 v16 extra and in episode 3 I try to load it won't appear in episode 3
Any save you make at any point during your ep2 v 16 extra version of the game will show up when you fire up ep3 as long as your ep3 is a 1080p extra version. The ep 3 version 8 extra hasn't been shared, only the 720p version 8 has. If you download the 1080p extra of version7 from the first page your saves from ep2 will show up.
Edit-
You could also manually move your 1080p saves to your 720p version.
Copied from the FAQ.
1.5.4
Q: Where to put the save files?
A: Win
720p C:\Users\%yourusername%\AppData\Roaming\RenPy\TestProj\
1080p C:\Users\%yourusername%\AppData\Roaming\RenPy\fashionbusiness1\
Mac
720p /Users/%yourusername%/Library/RenPy/TestProj/
1080p /Users/%yourusername%/Library/RenPy/fashionbusiness1/
Android
Android/data/com.fashion.business/files
1.5.12
A: Can i use my 1080p saves for 720p version of the game? I might not be able to hold on for much longer.
Q: Yes, you can use them. The only bug I know of (not critical for the game) is that on the first six saves of the game, the icons of your 720 saves may slightly overlap the 1080p icons of your old saves and this prevents you from seeing the interface arrows which are responsible for flipping through the save pages. The solution to this problem is very simple, you just need to save your 720p game in each of the 6 slots and the interface arrows will become visible again and you can continue to save your 720p game to any page.