Is it a vanilla resource pack or does it rely on Optifine? What incompatibilities are you experiencing and what version of Minecraft are you testing it in?
1.12 packs should work fine in 1.11. To make them work in 1.9 or 1.10 you just need to change the pack format in pack.mcmeta from 3 to 2. Going back to 1.8 use a pack format of 1 and you may also need to change models and blockstate files.
I Have made a resource pack for latest mc version 1.12.2 and it is not compatible with any other version of Minecraft,how can i make it compatible
Basically you need to make a different version for every single version of MC that you want to support. Or at least every MAJOR version. 1.12.0 and 1.12.2 play nicely, obviously, as do any where the only the third set of digits are changed. 1.11 and 1.12 also work together quite nicely, however 1.10 is different in some key ways so you'll need a different version of your pack even going that far back.
Sorry, but that's the nature of Minecraft. Updates give, and updates take away.