Is the two-rak'ah Ishraq prayer obligatory for one who sits in the mosque from the Fajr prayer until he performs the Eid prayer, or is the virtue achieved by performing the Eid prayer with the Muslims?

Ishraq Prayer is the same as Duha Prayer. It is performed after the sun has risen and ascended by the height of a spear, by one who sits remembering Allah after the Fajr prayer. Many scholars are of the opinion that the Eid prayer does not substitute for the Ishraq prayer. There is no harm in performing the Ishraq prayer before going to the Eid prayer, as long as it does not hinder one's preparation for it.