This feature is already there is most phones by going to:

1. Settings > Accessibility > Hearing > Flash Alerts
   
2. Toggle there to turn it ON/OFF. 
   

This is really beneficial in alerting without making any sound.

• Don't get dishearted if your phone does not have this feature. There are a number of apps available on Play Store.
  
• I'll personally recommend you to use the app named Flash Notification available in play store. It is really easy to use and you can enable it for particular apps and for different sound profiles(Ring/Vibrate/DND). 
  

You can also watch below video to help you activate the default feature:

You can check the complete product specs here: OnePlus 6T

Check the steps to insert sim:-

1. Ensure that the device is powered off.
   
2. Remove the Volume buttons/SIM tray (located on the right edge of the device).
   
3. Insert the SIM card into the tray.
   
4. Insert the SIM tray with the word UP facing the display side.

A video for your reference:

You can find complete specifications here:  Motorola One Power (P30 Note)

To buy Samsung Galaxy A7 2018 on EMI, you must have a credit card with an appropriate Credit limit. 

Then you can head to any online store like Flipkart and Amazon to buy your phone on EMI.

a. Open the App or website on your phone or PC

b. Then select the phone you want to buy and press buy now.

c. Select the Address and Tap on "Continue"

d. Select the "EMI" option as the mode of payment and Click on Continue.

e. Select your bank

f. Select the EMI time period from the options

g. Enter your card details and make to payment.

Check the complete specs here: Samsung Galaxy A7 2018

Motorola One Power (P30 Note) has a nonremovable battery so for any replacement you should contact to your nearest service center.

You can find a service center near you from here.

Method to change non-removable battery:

You can look at complete specifications here:  Motorola One Power (P30 Note)

Google Assistant Setup

1. : Long press home button to initiate the Google Assistant

2. : Tap "Continue" to go to your personal assistant screen

3. : The Tap on "Yes I'm in" to allow all the required permissions.

   Assistant Image

   Note: You can also be asked to activate the Voice assistant where you will be asked to record "Ok Google" three times.

   You can also watch this video for detailed information about Google Assistant 

   
   

   You can check the complete specs of this phone: Motorola One Power (P30 Note)

To root your phone manually, you need to turn on USB Debugging. 

1. Go to Setting, Find kernel version in About.
   
2. Tap it seven times, at which point you should see the message, "You are now a developer!" With that done, tap Settings, About Phone, Developer Options, and then tick USB debugging." Then tap OK to approve the setting change. 
   
3. Now turn it ON  in fastboot mode and unlock the bootloader.
   
4. Install a recovery to help you with flashing.
   
5. Flash a supporting custom ROM and gapps.
   

XDA Developers is a great site to help you with the process, support and Custom ROMs.

Check the below video for One click root method that works on many latest devices:

You can find all the specs here:  Motorola One Power (P30 Note)

To buy a phone on EMI, you must have a credit card with the appropriate Credit limit. 

Then you can head to any online store like Flipkart and Amazon to buy your phone on EMI.

a. Open the App or website on your phone or PC

b. Then select the phone you want to buy and press buy now.

c. Select the Address and Tap on "Continue"

d. Select the "EMI" option as the mode of payment and Click on Continue.

e. Select your bank

f. Select the EMI time period from the options.

g. Enter your card details and make the payment.

You can see detailed product specifications here: Motorola One Power (P30 Note)

Turn on Battery Saver on your Android phone:

1. Go to settings.
   
2. Then tap on Battery option.
   
3. Then Tap on Battery saver option
   
4. Then select the percentage at which you want to trigger the battery saver in your phone and you are Done.
   

You can also check the video below for more description

You can check the complete specs of this phone: Motorola One Power (P30 Note)

Check the steps below to backup your Android phone:-

1. Go to your Settings menu.
   
2. Scroll down and tap on System.
   
3. Go to Backup & Reset
   
4. Enable Data Backup and Automatic Restore
   
5. Also, keep your Google account synced for contacts and calendar.
   

You can see detailed product specifications here: Motorola One Power (P30 Note)

You don't need to enable VoLTE. Insert the Jio (VoLTE enabled) in any slot. By default, VoLTE will be active. If it is not, you can change the network preferences from Network option in settings.

1. Go to Settings > Call Settings (Sim and Network)
   
2. Tap Cellular networks > Enable Voice over LTE On/ Off.
   

Alternatively, 

1. you can simply dial *#*#4636#*#* 
   
2. Choose Phone information.
   
3. Click " Phone Information" and Toggle VOLTE Provisioned.
   
4. Restart the phone and you are done.
   

You can check the below video to get more clarity:

You can find full specifications here:  Motorola One Power (P30 Note)

Flash Notifications are used to give Flash Alerts when you get a Call / SMS. 

This feature is already there is most phones by going to:

1. Settings > Accessibility > Hearing > Flash Alerts
   
2. Toggle there to turn it ON/OFF. 
   

This is really beneficial in alerting without making any sound.

• Don't get dishearted if your phone does not have this feature. There are a number of apps available on Play Store.
  
• I'll personally recommend you to use the app named Flash Notification available in play store. It is really easy to use and you can enable it for particular apps and for different sound profiles(Ring/Vibrate/DND). 
  

You can also watch below video to help you activate the default feature:

You can check the complete product specs here: Motorola One Power (P30 Note)