The word ability doesn't have a past tense as it is a noun not a verb.
Yes, "could" is the past tense of "can." It is used to indicate past ability or past possibility.
I believe the past tense of can would be "could have" but I could be wrong.
Past tense gives a word or words the ability to sound as if done in the past. Such as "I am eating the chicken" turns into "I ate the chicken".
the past tense of am is was and the past tense of has is had
The past tense of "has" is "had" and the past tense of "have" is "had."
Was and were are both the past tense of be. The present tense is: I am he is you are they are The past tense is: I was he was you were they were
"will be" is the future tense of "be". The past tense of "be" is "was/were".
The past tense is she did.
The word "were" is past tense. It is the past tense of the verb "to be."
The past tense of "will" is "would". The past tense of "to be" is "was" or "were".
The past tense of "you will not" is "you would not."
The past tense is had.