Only races that were available in Vanilla.
No Pandaren [else warning].
No Worgen [else warning].
No Draenei [else warning].
No Blood Elves [else warning].
No Goblins [else warning].
No allied races (e.g., Void Elf) [else warning].
Only race/class combinations that were available in Vanilla (e.g., no Human Hunter, Night Elf Mage, etc.).
No Monks [else warning].
No Death Knights [else warning].
No Demon Hunters [else warning].
No Horde Paladins [else warning].
No Alliance Shamans [else warning].
No Warlock summoning. Warlock summoning ok.
Mage portals are allowed.
No Mass Rezzing.
No Bloodlust hunter pets (e.g., Core Hounds, Nether Rays, etc.).
No mounts until level 40 [else dismount].
Up to 60% speed mount at 40 [temporarily block Journeyman Riding].
Up to 100% speed mount at 60.
No flying mounts whatsoever [else dismount, and block Expert Riding].
No druid flight-form whatsoever [else shape-shift/cancel aura].
No "utility" mounts [else dismount/leave vehicle].
No mounts with vendors (e.g., Traveler's Tundra Mammoth).
No mounts with passenger seats (e.g., Mechano-Hog).
No water walking mounts.
Only zones that were accessible in Vanilla.
No visiting or taking portals to expasnsion zones or instances (e.g., Outland, Isle of Quel'Danas, Northrend, Mount Hyjal, Uldum, Twilight Highlands, The Maelstrom, Pandaria, Draenor, Broken Isles, Invasion Points, Kul Tiras, Zandalar).
No visiting future expansion starter zones (e.g., Eversong Woods, Gilneas, Ghostlands, Azuremist Isle, Bloodmist Isle, Kezan, Lost Isles, The Wandering Isle).
Only group with rule abiders.
No groups or raids with players not abiding by these rules (i.e., not in our guild(s)).
No Dungeon Finder [block tab].
No Raid Finder [block tab].
No Summoning/Meeting stones [else decline].
No leveling through Battlegrounds.
No Warmode.
No Blackwing Lair until player has downed every Molten Core boss.
No AQ20 until player has downed every Blackwing Lair boss.
No AC40 until player has downed every AQ20 boss.
Choosing a class spec is allowed.
No dual spec.
Re-spec at a class trainer is allowed.
No talents [block tab]. No talents until Molten Core set bonus.
No glyphs.
No heirlooms [else un-equip and check statistics].
No heirloom mount.
No PvP gear as it's far too easily obtained.
No spending honor.
No city tabards (e.g., Stormwind Tabard, Ironforge Tabard, etc.).
No armor reducing weapons (e.g., Annihilator).
No use of anything that increases experience gain (i.e., XP multipliers, e.g., WoW Anniversary gift, Holiday quests, Darkmoon Faire buffs, Recruit-a-Friend, potions, etc.).
No Auction House.
Trading may only be done with other players/alts abiding these rules (i.e., players the guild(s)).
No money (e.g., via trade or mail) with players/alts outside these rules.
No attachments (e.g., via trade or mail) with players/alts outside these rules.
No profession skill level above 300 [block Master skill level training].
No recipes/patterns above level 300 [block trainer offered skills].
No recipes/patterns from future expansions.
No Jewelcrafting [block trainer].
No Inscription [block trainer].
No Archeology [block trainer].
No reagent bank.
No Darmoon Faire profession quests.
No XP gain after level 60. See Behsten in Stormwind or Slahtz in Orgrimmar.
No transmogrifying [block tab].
No transmog appearances [block tab].
No pet battles [block tamer, block tab, and forfeit].
No toys [block tab].
Guild banking ok.
Blood Elves ok.
Dranei ok.
No flying except in Outlands at level 70.
No Druid Flight-Form except in Outlands at level 70.
No flying in Azeroth (Kalimdor and Eastern Kingdoms) whatsoever.
Visiting Outlands ok.
Visiting Eversong Woods, Ghostlands, Azuremist Isle, and Bloodmist Isle ok.
[After some interval,] visiting Magister's Terrace and Isle of Quel'danas ok.
No Karazhan until player has completed every Heroic Burning Crusade dungeon.
No Badge of Justice gear (e.g., from Shattrath vendors).
Items sold by the faction reputation vendors (e.g., Honor Hold, Lower City, etc.) that are gated by "reputation barriers" ok.
Honor gear may be allowed at level 70, but it will be limited. Season 1 gear will be allowed (i.e., "Gladiator", e.g., Gladiator's Plate Helm) along with that seasons off-pieces (i.e., "Marshal's").
No "Merciless", "Vengeful", and "Brutal" gear.
No honor tabards.
Jewelcrafting ok.
Recipes/patterns up to 375 ok.
No profession skill level above 375 [block Grand Master skill level training].
No XP gain after level 70.
asmongold: https://pastebin.com/y5imtWm0 "Project 60 Rules & Info"
r_projectsixty: https://www.reddit.com/r/ProjectSixty/comments/3tse89/rules/ "Reddit ProjectSixty"
wowhead_rpg: https://www.wowhead.com/returning-player-guide-changes-classic-vanilla "Wowhead Returning Players Guide"