I was taught like, one can switch "Could" with "Would Be Able To", in a sense of hypothetical usage, and the future in a past tense like this one below.
I thought you could catch it.
I thought you would be able to catch it.
Q.1) But, can you put "Would Be Able To" into the place of the "Could" which is a past form of can?
When I was young, I could touch a bug with bare hands.
When I was young, I would be able to touch a bug with bare hands.
Q.2) How about the polite version of can?
Could you do this for me?
Would you be able to do this for me?
I'm not worrying about the subtle nuance differences. I'm just worried that they can't be exchanged at all.