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.
NO!!! It is the past tense of the verb 'to have'. Present tense I have You have He/she/they have Past Tense I Had You had He/she/they had Future Tense I shall have You will have He/she/they will have Not the use of 'shall/will'
'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
This is the conditional tense. For "ser" it is "sería", and for "estar" it is "estaría". The one you use depends on context.
You can use "had to" to express obligation in the past.