Daled cosos m'akev each other?

Question

Are the four cups of wine that we drink at the Pesach Seder m'akev (bar) each other. That is to say, without all four cups, do the cups a person does drink count for anything?

However one will ask, "l'mai nafkah minah". That is, how could the four cups be "m'akev" each other and what difference does it make?

Obviously a practical nafka minah would be: If one does not have four cups, is there any point in drinking three?

Seemingly there could be another. It says in the Mishnah in the beginning of Arvei Pesachim that if someone doesn't have four cups they take from the "tamchui" (take from Tzedeka). If the person is only able to get two cups from Tzedeka and can't get all four, does he still take? Perhaps only when he'll get four and be able to fulfill the mitzvah in it's fullest would he take from tzedeka.

As always provide sources and perhaps other nafkah minei for this question.

Answer 1

The Gemora in Pesachim 109b states: "The Rabbis enacted that we drink four cups of wine as an expression of freedom, and each is an independent obligation." Based on this, the Rashash there writes that the four cups are not "me'akev" each other.

The Magen Avraham (472:14) rules that if one has only four cups of wine for the entire Pesach, they should use it all for the first night and not leave half for the second night "because the first night is more important". The HaSeder Haaruch (47:1 footnote 2) writes that from here it seems evident that if not for the reason that "the first night is more important" he should have drunk two cups each night - and we don't say that it's either four cups or nothing.

However, the Maharal (Gevuros Hashem chapter 49) writes that if one does not have all four cups he does not need to drink at all, and the Gemora only meant that each cup has it's own independent reason but they are all one combined obligation.