How to build read-only image using OpenWrt?

i want to build an image that is read-only. anyone have an idea how to archive this?

the openwrt image is by default read only, the config, addon packages, etc are however written to a rw part of the flash.
what do you trying to achieve ?

i want this

no one able to create , delete or write any file

There is no turn-key solution for that.

but some routers have .... is their any way to do this?

Only if you develop it on the source level.

the next question is then obviously, is the screen shot posted, from stock openwrt, running on a supported device ?

no someone post it on form and he wants to recover file system from read-only .

While not a 'proper' way to achieve the goal... if the device in question has a limited amount of flash storage, you could just fill it up to the maximum size allowed for the image targeting your device. If there is literally no space, the filesystem won't have enought space to actually write any files (it might even end up mounting a read oly partition.

or generate an image with no free space, not filling the full flash.