it is not possible because estar is temporary so there is no way that you can
You use the past tense form which is 'had'.
Is can be used in the past tense if it's in its past tense form, which is was.
"is' is present tense. For past tense use was or were.
I used the past tense to answer this question.
The past tense is involved.
'Who' is a pronoun, it doesn't have a past tense. But you can use the word "was" as in "who was on the phone?".
No. The word "are" is present or future tense. The past tense would be "were".
To is not a verb and does not have a past tense.
Would is the past tense for will
You can use "had to" to express obligation in the past.
you could use it in the future tense e.g i will be getting a hamster on saturday. for the past tense you would use been. for the present you could use something like doing
This is the conditional tense. For "ser" it is "sería", and for "estar" it is "estaría". The one you use depends on context.