Dought & clear - What is the ruling on offering the regular Sunnah prayer that is usually offered after the obligatory prayer, before the obligatory prayer?

Is it permissible for someone to pray the 2 unit of sunnah of esha
salaah beforehand of the obligatory prayer ? If someone prayed it
without knowledge about the ruling, what is the stand ?
Praise be to Allah.
The regular Sunnah prayers are of two types:
1.The Sunnah prayers that are offered before the obligatory prayer.
They are: two rak'ahs before Fajr and four rak'ahs with two tasleems
(i.e., offered two by two) before Zuhr.
The time for this type of Sunnah prayer begins when the time for that
prayer begins, and lasts until one begins to offer the obligatory
prayer.
2.The Sunnah prayers that are offered after the obligatory prayer.
They are: two rak'ahs after Maghrib, two rak'ahs after 'Isha' and two
rak'ahs after Zuhr.
The time for this type of Sunnah prayer begins when the obligatory
prayer is over and lasts until the end of the time for that prayer.
Ibn Qudaamah (may Allah have mercy on him) said: With regard toevery
Sunnah prayer that is offered before the obligatory prayer, itstime
lasts from the beginning of the time for that prayer until the start
of the obligatory prayer. With regard to every Sunnah prayer that is
offered after the obligatory prayer, its time lasts from when that
prayer is finished until the end of that time.
End quote fromal-Mughni, 1/436
It says inal-Mawsoo'ah al-Fiqhiyyah(25/281-282): The regular Sunnah
prayers are connected to the obligatory prayers; someof them are
offered before the obligatory prayer, such as the Sunnah prayer of
Fajr and the Sunnah prayer that comes before Zuhr. And some of them
are offered after the obligatory prayer, such as the Sunnah prayer
that comes after Zuhr, the Sunnah prayers of Maghrib and 'Isha', Witr,
and qiyaam in Ramadan (i.e., Taraweeh).
With regard to whateverof these Sunnah prayers come before the
obligatory prayer, the time for them begins when the time for the
obligatory prayer begins, and ends when the iqaamah for the obligatory
prayer is given, if that iqaamah is given in a group or congregation
(jamaa'ah), because once the iqaamah is given for prayer, there isno
prayer except the prescribed obligatory prayer. But if an individual
is going to offer the prayer on his own, the time for the Sunnah
prayer lasts untilhe begins the obligatoryprayer.
With regard to the Sunnah prayers that come after the obligatory
prayer, such as the Sunnah prayer that comes after Zuhr and the Sunnah
prayers of Maghrib and 'Isha', the time for each of them begins when
the obligatory prayer has been completed and lasts until the time of
theobligatory prayer ends and the time for the nextprayer begins.
End quote.
Based on the above, if a person offers the Sunnah prayer that should
be offered after 'Isha' before he prays 'Isha', it is as if he has
performed that Sunnah before its time. Hence it will not be counted as
a regular sunnah prayer; rather it is a naafil prayer between the
adhaan and iqaamah, for which one earns the reward of a naafil prayer,
not a regular Sunnah prayer.
An-Nawawi (may Allah have mercy on him) said:It is mustahabb to pray
two rak'ahs or more before 'Isha', because of the hadeeth of
'Abdullahibn Maghfal, according to which the Prophet (blessings and
peace of Allah be upon him) said: "Between each two calls (the adhaan
and iqaamah) there should be a prayer, between each two calls there
should be a prayer, between each two calls there should be a prayer" –
and the third time he said, "for whoever wishes." Narrated by
al-Bukhaari and Muslim. What is meant by the two calls is the adhaan
and iqaamah, according to scholarly consensus.
End quote fromal-Majmoo', 3/504
For more information please see the answer toquestion no. 128164
With regard to the one who used to do that andwas unaware of the
ruling as mentioned above, then we hope that Allah, by His bounty and
grace, will grant him the reward of one who offered the regular Sunnah
prayer, because he was unaware of the ruling on that matter.
And Allah knows best.