how can we make Iris variant to decor some stragates variants or control iris via CC:tweaked ?

Iris can be controlled with CC:tweaked
check changelog for 0.6.31
https://www.curseforge.com/minecraft/mc-mods/sgjourney/files/5726465/changelog

About iris variants
I think they are "item controlled", so all you need to do is provide a texture with a resource pack and refer to that texture from item NBT.

example: golden iris item with netherite texture when placed on gate (code)
/give @s sgjourney:golden_iris{texture:"sgjourney:textures/entity/stargate/iris/netherite_iris.png"} 1

Also, I suggest using GitHub discussions for general questions unrelated to mod issues.
Or join Discord instead: https://discord.gg/VDSqzdBqRd

how the "closeIris()" and "openIris()" function ?

closeIris() starts closing the iris

openIris() starts opening the iris

Of course, it works only when the iris is installed on the gate.

like this ?

interface = peripheral.find("crystal_interface")
interface.closeIris()