How to deal with multiple aspect ratios

Hi, I’m developing a 2D puzzle like game. I want to target all iOS devices (iphone 4+ ,ipad 2+ and retinas) and as much android devices as possible. The problem is as you already guessed with resolutions and aspect ratios. How to deal with it, and what are the best practices. please share your experience and best approaches with this problem.
My approach is , I’m building for 3:4 (the game is in portrait mode) aspect ratio with ipad retina resolution images and using orthographic camera.
for different aspect ratios i resize orthographic camera , and as expected I get black bars at the top and bottom . aka pillarbox. so I’ll just resize (scale Y) the main scene. (drop everything in an empty gameObject and scale it up). or add 2nd camera to deal with this black bars.
But I need the best and the most correct way to deal with this problem , what’s the best practices for 2D game development when targeting multiple resolutions,aspect ratios. I’ve searched the net and forum but couldn’t find the CORRECT WAY.

The correct way is to consider the different aspect ratios at which your game will be played, and implement a strategy for how your game will be rendered for those aspect ratios. The three cases you need to manage aspect ratio for are your Game view, UI view, and zoom.

Firstly, letterboxing or pillarboxing your game view is 100% OK and windowboxing in exchange for pixel perfection is also 100% OK. Mobile games especially tend to have an approach of “I support aspect ratios in this range, and any additional pixels aren’t used”. The black bars can also be substituted for more thematic, non-black bars, i.e. have a background that occupies a much larger area than your default game screen. Fruit Ninja is an example of a game that has a custom pillarbox. In addition, an extra-wide screen could give a player a vision advantage which is arguably unfair so many games have a field of vision limiter which serves as a strategic element.

Secondly, consider how your UI should change in appearance due to device aspect ratio, which can range from a game score to a complex menu. Mounting a panel to the top right corner for example may give bad results on an ultra-wide screen. The most flexible solution is to render your UI using a separate camera. As an aside, your splash screen and opening menu are the easiest parts of the game for you to make aspect-ratio agnostic, as they are often separate scenes with fairly simplistic elements.

The final thing to consider, especially for mobile, is whether and how to handle zoom. Zoom is a powerful feature which engages a higher percentage of the pixels on screen to make your game more visually comprehensible. Implementation is highly game-dependent but is worth considering.

Fine-tuning specific components is beyond the scope of this answer, but as long as you handle these three cases your game should end up aspect-ratio resilient.