Best way to update Support Library

Question

Till now(30-Nov-2017) google has released android support lib version 27.0.2 and Android Api version 27(Preview). Right now my application have Target version 25 , Build tool version 25.0.3 and Compile sdk version 25. I am planning to update my Support Lib as well as Compile sdk version to 26. So my questions are
1. Is Support lib version is related to android Api version means I am not updating android api to 27 because it is in preview so should I uses support lib 26.x.x or 27.x.x(which is latest).
2. which build tool version should i use means

Answer 1

Go for API level 26. Because API 27 is in preview mode so it won't be stable for now. Change your Build.gradle file like this and sync you are good to go.

android {
compileSdkVersion 26
buildToolsVersion "26.0.3"
defaultConfig {
    applicationId "Your app ID"
    minSdkVersion 16
    targetSdkVersion 26
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner 
   "android.support.test.runner.AndroidJUnitRunner"

}

And you will have to update your dependencies too because they won't work in latest versions if you use the old ones. So that's why supp lib is related to android API.

implementation 'com.android.support:appcompat-v7:26.1.0'
implementation 'com.android.support:support-v4:26.1.0'
implementation 'com.android.support:design:26.1.0'