Iranians have begun to regain internet access after authorities ended a monthslong shutdown. But users say service is slow and spotty in some areas, with apps like YouTube and Instagram heavily restricted, as they were before the cutoff began during nationwide protests in January. Authorities justified the outage as a military imperative after the United States and Israel attacked Iran on Feb. 28. Their decision to lift some restrictions this week came as negotiators appeared to be closing in on a more permanent truce. But many Iranians feared access could be cut off again at a moment’s notice.