Unresolved reference: kotlin_version

[AnandDangwal]

"buildscript {
ext.kotlin_version = '1.5.31'

...

}
ext {
activityVersion = '1.4.0'
appCompatVersion = '1.4.0'
constraintLayoutVersion = '2.1.2'
coreTestingVersion = '2.1.0'
coroutines = '1.5.2'
lifecycleVersion = '2.4.0'
materialVersion = '1.4.0'
roomVersion = '2.3.0'
// testing
junitVersion = '4.13.2'
espressoVersion = '3.4.0'
androidxJunitVersion = '1.1.3'
}"

Inside buildscript block it is showing an error which is "Unresolved reference: kotlin_version" , I don't know why.
Same error is showing in the 'ext' block "Unresolved reference" for all variable . But I have solved by changing androidxJunitVersion = '1.1.3' to var androidxJunitVersion = "1.1.3" for each variable.
When I resolved the unresolved reference error then It is showing me <Variable 'appCompatVersion' is never used > this is showing for each variable in the 'ext' block.

[AnandDangwal]

These are the screen shot of my build.gradle.kts(app) and buld.gradle.kts(project) file . I thought this might help you understand the problem.