All depend on which server you are currently playing.
On FICS, any help are illegal. That include: engine help, opening book, human help, endgame table ,etc. So during a suicide game on FICS you cannot look at the opening book or the endgame section. You can use suicidechess project to learn where you had blunder in a previous game.
I think that same rules apply to ICC server, but I’m not sure yet.
On SchemingMind, it’s bit more complicated. You can use opening book, and any chess book. You cannot use any human help and engine help. So yes, you can look in our opening section, but it’s illegal to raise some position’s priorities since positions are evaluated by a engine. IMHO, I found strange that you can look some every depth line (many lines goes father than 50 ply), but according to SchemingMind rule, you still have the right to look at it.
I know, that on any chess server, there will be some cheating humans. Most of them do it knowing that’s cheating, and sooner or later they got caught. In the suicide variant it’s even easier to caught cheaters, since there’s fewer engine and website.
If you are host a chess server supporting suicide variant, and want to know if a player is cheating or if you’re a player, and wanted to know if your opponent had cheated. I can help…