I had a confusion between Infinitive form of the verb and the base form of the verb. But this LINK explains the difference between infinitive and base form of the verb.
Base form: be, have, hold, sleep, dream
Infinitive form: to be, to have, to hold, to sleep, to dream
Can we write all helping verbs in infinitive form which are mentioned below:
- be (including am, is, are, was, were, been)
- have, has had
- do, does, did
- can
- could
- may
- might
- will
- would
- shall
- should
- must
I know these exists to be, to do, to have, but do others?
am, is, are, was, were, been
these are the "be" forms. Hence they will not have "to" as the prefix.