Blessing on Esrog:
Esrogim that are only mildly sour and are thus edible receive the blessing of Shehakol. Esrogim that are very sour to the point of inedibility do not receive a blessing at all prior to consumption.
Esrog peel: The raw peel of an Esrog which is edible receives the blessing of Shehakol prior to consumption. If the peel was turned into marmalade or a chocolate covered treat then its blessing is Haeitz.
Shehechiyanu: The blessing of Shehechiyanu is not recited upon eating an Esrog.
 Luach of Rav Prus; So rule regarding lemons: Ketzos Hashulchan 49/16; Brachos Guide in English Birchas Hanehnin; Brachos guide of Rav Prus; Seder Birchas Hanehnin 6/22 of Rav Elyashvili footnote 130 and in his Luach; See Piskeiy Teshuvos 202/35; Also, see Luach of Rav Elyashvili in Seder Birchas Hanehnin that an edible raw Esrog is Haeitz. This contradicts the rules that were taught in Admur and Poskim ibid regarding fruits that are not planted to be eaten in their current state.
 The reason: As these fruits are edible in a time of need and thus they receive a blessing. [See Admur 202/4; Seder 6/1; Ketzos Hashulchan ibid and 49/7] However, their blessing is Shehakol, as all fruits that are not commonly planted to be eaten receive the blessing of Shehakol. [Seder Birchas Hanehnin 6/22; Luach 9/9; Admur 203/6 and 204/3-4 and 205/1; M”A 203/4]
 See Admur 202/4; Seder 6/1; Ketzos Hashulchan ibid and 49/7; Michaber 202/2; Birchas Habayis 1/49; Piskeiy Teshuvos 202 footnote 96
 See Admur 202/9; Seder 6/4 and 15; Ketzos Hashulchan 51/7 footnote 7
 Orchos Chaim 202/9 in name of Minchas Pitim Piskeiy Teshuvos 202/13 footnote 67; Luach of Rav Prus; Luach of Seder Birchas Hanehnin in English; Luach of Rav Elyashvili in Seder Birchas Hanehnin
The reason: Esrog peels that are in jam or candy or chocolate are Haeitz as a) they are cultivated for their peel, and b) the peel is the main part of the fruit. [Poskim ibid based on Ran Shabbos 108; See Admur 202/9; Seder 6/4 and 15 that the only reason a peel is degraded from its blessing is because it is not the main part of the fruit, and hence by an Esrog, since it is the main part of the fruit its blessing is Haeitz.
 Poskim in Piskeiy Teshuvos 225/17 footnote 124