There are so many different aspect ratios, and so many devices with said aspect ratios, it would be a bear impossible task to compile data on every device on the market, off the market, and future market, so it's better just to support the most common ratio and adjust to suit all (though it will look slightly different on each device that's not your set aspect ratio).

This will only really be the amount of background that can be seen. UI elements can remain fixed in their respective positions.

I get what your saying but there's no need to offer different resolutions as a setting within your game. Just stretch your background around 20% larger than your viewport and use scale inner/outer (depending on your game, UI etc) and you'll be set for multiple ratios.

And as I said, you can always use Scale Layout if you want to give the appearance of being zoomed in or out within your game

Viewport size is fixed unfortunately. You can however use Scale Layout to zoom in/out of your layout giving the effect your after

16:9 is the most common aspect ratio on mobiles but a lot of manufacturers are going wider. My preferred way of going about this is scale inner/outer depending on the game. Expand your backgrounds about 20% wider than your viewport and you'll cover most odd resolutions that Xiaomi (in particular) like to use.

Compress every image/sprite whenever you add one to the game! Need to keep that package size down, and it helps with performance on lower end devices. It'll save you hours of work in the long run.

Don't over complicate things or it won't run well on old devices - or at all. I have a huge 70% crash rate or ANR rate on Android 8/9 due to the amount that's going on in one of my games - even with a low performance button (disables lighting, shadows, effects etc) the game can be very choppy on lower end devices (even if they are modern).

This is data saved for your device only. Unless the highscores are on a server, then none of the data you've had stored on your device will be transferred over. If you want to start the game afresh on your device go on settings - apps - app name - clear cache and data

Also worth noting it was a bank holiday for the Queens funeral yesterday and pretty much all of the UK was closed. Even McDonalds was closed!

It's a bit more work but you can check purchases server side with Validator URL

Do you mean that if a user goes to purchase the IAP and decides not to go through with the purchase, they are still getting the purchase or do you mean if a user purchases an IAP and the purchase is complete, then later files for a refund?

Sadly, not much you can do if they buy then get a refund. There are many high profile MMOs that offer IAP in the region of $100 per purchase who suffer from chargebacks etc. The only way they can combat these is to close the player accounts.

It's the same with Steam - users purchase a game, if they don't like it or can complete it within 2 hours, they simply get a refund. Free game for them, Dev loses out

You need to keep your UI in the Viewport. You can also use the Anchor expression to keep them in the same position at all times, regardless of the aspect ratio of the devices screen

As far as I know the viewport size can't be changed from the parameters set in the project properties. Best bet if you want to alter the amount of the layout you can see is to use LayoutScale

Is it 2d or 3d? If you can, replace the objects with a tilemap. You can customise the collision box for each object and it'll take up way less resources. Compress your images at somewhere like tinypng to save more resources. If your only running at 18FPS on PC then your going to have a hard time later down the line of you add a player, enemies with behaviours etc. If your aiming for mobile then it's only ever going to run on top end devices

I don't think vibration works in debug, try a signed or unsigned package and test that

It looks like it's been changed since I made that game. You could try "tag for under age consent"

Indicate the user should be treated as under the age of consent as per the restrictions in the European Economic Area(EEA) General Data Protection Act(GDPR). This action is not supported in web exports.