The player #ID can be found in the Progression menu under your username, by clicking on your profile card on top left of the main menu.
If instead of your player #ID it shows localuser, then you need not connected the game to your Google Play Games/Game Center account from the game settings.

This game uses a cloud save system that is updated each time you play when connected to internet.
In order to get your savefile updated to the cloud, you need to connect your game to Google Play Games/Game Center into the game settings.
To recover your data, simply connect your game to the same Google Play Games/Game Center account and the game will restore your last savefile.

Download and install Google Play Games from the Play Store.
Launch Google Play Games and connect to your account or create a new one.
Relaunch the game and go to the settings menu, press the connect button under Google Play.
The game will reboot and ask to select your Google Play Games account.

Go to your iOS device Settings and activate Game Center, create an account if needed.
Relaunch the game and go to the settings of the game, press the connect button under Game Center.
The game will reboot and automatically connect to your Game Center account.

The VIP status is a sort of thank-you-item for supporting the game, it gives you access to a dedicated leaderboard.
It also gives you a VIP emblem displayed on your profile, visible in the leaderboards and result screens to all players.

If you attempted to purchase an item and that your order has been canceled, your order will not be charged.
If you order has been charged but you didn't received your item, you can manually try to unlock it by buying the same item again, your item will be unlocked without any further payment.
If you still haven't received your item, please contact us by email with your order invoice and your player #ID.

Normally, you receive the purchased items immediately, but sometimes it can takes longer. If it happens, it's because the purchase is still being processed.
If you've waited more than 24 hours and haven't received anything, please contact us by email with your order invoice and your player #ID.

All you need to do is to link your main account to your secondary account, for example, from your Android device to your Xbox.
Launch the game on both devices, then go to settings and press Accounts linking.
On your Android device select Generate to generate your account linking password.
Then copy this password in the field on your Xbox (the password expires after 3 minutes), the game will reboot and your accounts will be linked.

If you've correctly entered the player #ID but you still get an error message like No record found, it's because the player you're looking for has not registered any score into the leaderboard yet.
Your friend will need to win a ranked Firefight game in order to join the leaderboard, then you'll be able to add him to your friend list.