QUICK EASY RULES:
There must be Thirty-One horror films

Fourteen Countries:
Argentina = When Evil Lurks
Canada = Ginger Snaps
France = Diabolique
Germany = The Eyes of the Mummy & Vampyr
Guatemala =  La Llorona
Italy = The Whip and the Body
New Zealand = Braindead
Norway = Dead Snow
South Africa = Good Madam
South Korea = Train to Busan
Soviet Union = Viy
Spain = [REC]
United Kingdom = The Devil Rides Out & The Wicker Man
USA = The Addams Family, Altered States, Anaconda, Arachnophobia, Blacula, The Crazies, Dawn of the Dead, The Funhouse, Halloweentown, Night of the Comet, A Nightmare on Elm Street 3: Dream Warriors, The Picture of Dorian Gray, The Sacrament, Twin Peaks: Fire Walk with Me, The Unknown & The Wizard of Oz

Twelve Decades:
1910’s = The Eyes of the Mummy
1920’s = The Unknown
1930’s = Vampyr & The Wizard of Oz
1940’s = The Picture of Dorian Gray
1950’s = Diabolique
1960’s = The Devil Rides Out, Viy & The Whip and the Body
1970’s = Blacula, The Crazies, Dawn of the Dead & The Wicker Man
1980’s = Altered States, The Funhouse, Night of the Comet & A Nightmare on Elm Street 3: Dream Warriors
1990’s = The Addams Family, Anaconda, Arachnophobia, Braindead, Halloweentown & Twin Peaks: Fire Walk with Me
2000’s = Dead Snow, Ginger Snaps & [REC]
2010’s = La Llorona, The Sacrament & Train to Busan
2020’s = Good Madam & When Evil Lurks

Five Zombie Films = Braindead, Dawn of the Dead, Dead Snow, [REC] & Train to Busan

Three cult or conspiracy horror films = The Devil Rides Out, The Sacrament & The Wicker Man

One film from a Black director with a Black lead = Blacula

One film from a Mexican or Central American director = La Llorona

One Canadian film = Ginger Snaps

One Russian or former Russian state film = Viy

The most popular film from the 1940s that you haven't seen and can access.. = The Picture of Dorian Gray

Two Post Apocalyptic horror films = The Crazies & Night of the Comet

One Film with dreams or a dream as part of the plot = A Nightmare on Elm Street 3: Dream Warriors

One The animals are pissed at us film = Anaconda

Two Silent film = The Eyes of the Mummy & The Unknown

Six based on Novels = Altered States, The Devil Rides Out, Diabolique, The Picture of Dorian Gray, Vampyr & The Wizard of Oz

Any film from THIS list (List provided in the link) that you haven't seen = Altered States

One Ernesto Gastaldi written film = The Whip and the Body

One film from 1932 = Vampyr

I have never made a specific film a part of this before, but WIZARD of OZ ('39) = The Wizard of Oz 

And one Tobe Hooper Film (There must ALWAYS be a Hooper film) = The Funhouse