He entered ihram for ‘umrah at the end of Sha’baan and performedit in Ramadan; will he have the reward of ‘Umrah in Ramadaan?

A man entered ihram for'umrah before the adhaan for Maghrib on the
last day of Sha'baan, and after Maghrib it wasannounced that Ramadan
had begun. Will his 'Umrah be counted for him as being in Ramadan or
not? In other words, he formed the intention to enter ihraam before
Maghrib, and he did 'Umrah that night, i.e., the first night of
Ramadan.
Praise be to Allaah.
'Umrah in Ramadan brings a great reward, which is the reward of Hajj.
It was narrated from Ibn 'Abbaas (may Allah be pleased with him) that
the Messenger of Allah (blessings and peace of Allah be upon him) said
to a woman of the Ansaar: "What kept you from performing Hajj with
us?" She said: We only have two camels and the father of her sonand
her son had gone for Hajj on one camel, and he left us the other camel
so that we could carry water on it. He said: "When Ramadaan comes, go
for 'Umrah, for 'Umrah in (that month) is equivalent to Hajj."
Narrated by al-Bukhaari (1782) and Muslim (1256).
In order for the Muslim to attain that great reward, he has to enter
ihram for 'umrah and perform the rituals in the month of Ramadan. He
cannot enter ihram for it on the last day of Sha'baan, even if he
performs its rituals in Ramadan, and he cannotenter ihram for it in
Ramadan and perform the rituals in Shawwaal.
There are two ways of performing 'umrah that do not bring the reward of Hajj:
1 – Entering ihram for 'umrah at the end of the month of Sha'baan and
performing the rituals after the month of Ramadan begins.
2 – Entering ihram for 'umrah before the sun sets on the last day of
Ramadan and performing the rituals on the night before Eid.
Shaykh Muhammad ibn Saalih al-'Uthaymeen (may Allah have mercy on him) said:
For the person who does'umrah in Ramadan it is essential that his
'umrah -- from entering ihram until the end of it -- should be in
Ramadan. Based on that, let us lookat another example:
If a man reaches the miqaat in the last hour of Sha'baan and enters
ihram for 'umrah, then the sun sets and Ramadan begins with the
setting of the sun, then he comes to Makkah and does tawaafand saa'i
and cuts his hair, can it be said that he did 'umrah in Ramadan?
The answer is: No, because he started his 'umrah before the month of
Ramadan began.
A third example: A man entered ihram for 'umrah before the sun set on
the last day of Ramadan, and he did tawaaf and saa'i for 'umrah on the
night before Eid. Can it be said that he did 'umrah in Ramadan?
The answer is: No, because he did not do 'Umrah in Ramadan, as part of
his 'umrah was done outside of Ramadan. 'Umrah in Ramadan is that
which lasts from the start of ihram to the end (in Ramadan). End
quote.
Majmoo' Fataawa al-Shaykh al-'Uthaymeen, 21/352, 353
And Allah knows best.