Between "Yishtabach" and "Yotzer Or"

If I finished Yishtabach and the kehila Is up to Kaddish of after Rabbe Yishamael Omer, can I answer to the full Kaddish?

Shalom!

Thank you for your question.

As you know, the morning prayer, Shacharit, begins by praising Hashem and only afterward do we make our requests of Him. The Talmud (Berachot 32a) teaches us that this sequence of events is derived from Moshe Rabbeinu who first praised Hashem (Deuteronomy 3:24), “Hashem, God, You have begun to show Your servant Your greatness and Your mighty hand. What force is there in heaven or on earth that can perform deeds and mighty acts as You do?” and only afterwards did Moshe plead, “Please let me cross [into the Land of Israel] so that I may see the good land…”

So to answer your question, yes, you my answer Kaddish after having concluded “Yishtabach” and before beginning “Yotzer Or.”

For the benefit of readers let’s review more of the rules that apply when one is between “Yishtabach” and “Yotzer Or.”

It is permitted to respond to any congregational response, including “Amen” and “Baruch Hu U’varuch Shmo.” For example, one may respond to the entire “Kedusha” on both Shabbat and weekdays and the “Modim Derabanan.” One who was not yet wearing Tefillin may put the Tefillin on at this time and recite its accompanying blessings.

So too, one who skipped parts of Pesukei D’zimra in order to catch up to the congregation but then realizes one has more time before “Barchu” may recite the passages that were skipped.

One may not recite the “Brich Shmei” if the Torah is being removed from the Ark, and as well not  “Vezot Hatorah...” if the Torah is lifted during this time.

If one is the only Kohen or Levi in the congregation then he should leave the shul if however, they call him then he may accept the Aliyah.

In an emergency, one may also speak during the time if doing so is needed in order to prevent a loss.

OC 51, 53, 54, 66 with commentaries