How to do Unlockable Items for a Character Collection Clicker Game? How to disable buttons?

Question #1

Basically I want it so that after a person has clicked enough, they can see what their new character is.
I'm guessing this has to be done with raycasting, but I'm really confused by the whole raycasting and colliders thing? Does anyone have anything to point me in the right direction?
All the video tutorials I was finding on it have to do with colliding with an enemy.
But I want a mouse button click to do that.
When the mouse clicks the "Collect button", I need more than just the button itself to disappear.


Question #2

The buttons I have labeled at Rate x# increase the players Count per Second, but I only want them to be able to click each one once per character they've collected.

As well as have the scroll bar under the text staying at 100% and having it's color change after the click. (and possibly text, but the text changing isn't an important must have for me.)


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Thanks if anyone can help!~