Sorry, my English is bad and perhaps misunderstood. This saying should use the device you want to use or smaller and go climbing up bigger size?
In my case I have made the game 790x1280 and should do to make it look in 480x800? I redo all?
Another problem I have is that if I use size iphone 6 in many cases is not compatible mobile android and out of position ... that headache
No.... its good , if your game is 790x1280 then u are on high scale quality graphics however not sure if the 790x1280 will match perfectly in 480x800 when re-scaled, you should check screen size resolutions on google, if ur game is built on high resolution is good
The bad part wold be when u build your game on low scale resolution(like 480x800) and u need to stretch to higher displays(like 790x1280)
so i think ur good , however if ur still experiencing downscale problems sharp edges, make sure all the settings are set to high i wold change the sampling from point to linear, which will give u a better image processing i think, have to check the manual on that.
in order for saving some image processing power, i wold disable the webgl.. if you dont have any webgl effects inside or blend mods on sprites.
that will give u a faster image processing on some older devices.
if your client still has problems with the edges, make sure the graphics have no sharp edges in the original format, outside then that, it only depends on the device capabilities.
make sure for ios u dont use any webgl effects, they are not handled that well by iPhone's, since apple introduced webgl support only in early ios8 release but that was for ads, not for games, so im not sure if they added webgl support in ios9 and above for in-game effects.... unless apple updated their platforms software's.
for android not sure if webgl really matters, but if you dont have need of webgl dont use it.
its pointless to have it enabled if you dont use it, and also seems that Kyatric gave you the reason why this happens, isn't meant for android 2.3 but for 4.0 and above.
it might also be a compiler problem, what do you use ? cocoonjs? phonegap? intelxdk?
also you should read the tips from Kyatric since is an official moderator.