Q. In order to comply with Hallel at the seder, does one need to say every word? This is a problem as at that time people may be falling asleep, especially the elderly. If one did not comply with Hallel, is one also not yotzi the fourth kos? Thus, one who cannot or will not say every word of Hallel, there is no point in drinking the fourth cup?
Or he should say as much as he can and drink?
A. Tosafos (Brochos 14a d'h Yomim) mentions that we don't recite a prior brocho on the Hallel of the Haggada since it is interrupted by the meal.
Horav Shlomo Miller's Shlit'a opinion is that the although no brocho is recited for this Hallel, one should still be careful to say correctly every word, and if mistakes or omissions occurred, one has to repeat. However, even if the Hallel was deficient or omitted, one complies with the fourth cup when one drinks it.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit'a