How would you like Sonic and other characters to aquire new abilities in games?

[Shiny Gems]

Yeah, the title is pretty much what this thread is about. This is about character specific abilities, not really items that grant abilities like the Elemental Shields from Sonic 3 and Knuckles and the Chaos Emeralds from Sonic Superstars.

Now, in games like Sonic Unleashed, Sonic Adventure 1 and 2, those games had basically areas with the item needed for a new ability each character could collect in order to gain a new ability.

Also, in Sonic 06, you had to pretty much buy abilities from the store. You had to collect a number of rings, go to a TV monitor, select what you want from it and the store and there is that.

Now, for reference on another method of gaining abilities, check this out.

This is an idea for a game, fan game or whatever that would never come out. In it, the three playable characters; Sonic, Tails and Knuckles, could gain different abilities from different characters, kind of like in Mega Man. However, it is not just having to defeat these characters in a fight to get these abilities, but this would also be in terms of racing them, saving them, doing something with them, and the like.

Also, there is the option of beating actual bosses to get the ability. This method is not just from Mega Man, but also from Crash Bandicoot 3 and Crash Bandicoot: Wrath of Cortex. Take a look here.

With that, getting enemies from bosses would ideally be in boss only levels or Act 2 or 3 bosses, not just in any level.

There is also getting abilities from missions, like in Sonic Generations with its mission and the skills you get from some of them, or Sonic 06, where at the beginning, you had to get the Custom Shoes for Sonic from one of the first missions available in his episode. You just had to complete the missions and you would gain new abilities in some way.

Also, in terms of Sonic Unleashed, in terms of the Werehog and maybe the game called Sonic and the Dark Brotherhood; simply level up to learn new abilities that you are able to use in levels.

Or, in terms of Sonic Forces, there is the most simplest way coming from the Avatar character; just have the abilities from the beginning instead of working for them.

With all that said, I would like to ask; which one of these methods of gaining abilities would you prefer to be had in the games? If there is a different method you would like to see not listed on here, please describe it.