The Elder Scrolls IV: Oblivion Remastered

For a forgiving first playthrough, run a Spellsword: Breton race + The Lord birthsign stacks to 65% magic resistance at level 1, paired with Major skills in Blade, Block, Heavy Armor, Restoration, and Destruction. Pump Strength, Endurance, and Willpower at every level-up. Custom class is the way — Oblivion's leveling system rewards specific Major skill choices, so don't pick from the preset templates. Start in the Imperial City after the tutorial and level cautiously to avoid the infamous enemy-scaling spiral.

Source: Yardbarker Build Guide

Oblivion Remastered keeps the original's five-tier slider (Novice / Apprentice / Adept / Expert / Master). Adept (default) is forgiving for new players but trivializes mid-game; Expert jumps to a punishing 3.5× damage taken multiplier, which catches most players off-guard. The recommended approach: stay on Adept until your first major dungeon or Oblivion Gate feels too easy, then bump to Expert. You can change difficulty mid-fight without penalty, so feel free to drop down for tough encounters.

Source: TheGamer Difficulty Guide

A few stand out: defeating Agronak gro-Malog (the Gray Prince) before completing the "Origin of the Gray Prince" questline locks you out of his permanent Gray Prince's Training ability and makes his Arena fight harder. In the Shivering Isles expansion, the Mania-vs-Dementia ruler choice is one-shot and decides which achievement and Ring of Lordship enchantments you get. Most main-quest-aligned content is recoverable, but Dark Brotherhood and Thieves Guild questlines have permanent failure states if you violate code-of-conduct rules mid-quest.

Source: Game8 Missables List

No — every Elder Scrolls game tells a self-contained story in the same world, with only loose lore connections between them. Oblivion's plot stands alone (Daedric invasion, Oblivion Crisis, Septim succession), and the gameplay foundation is fully tutorialized. If you've played Skyrim and want the prequel context, Oblivion shows the political setup that leads to the Empire's fragmentation 200 years later, but it's flavor, not requirement. Newcomers can start here cold.

Source: Wikipedia

An enormous amount. The main Oblivion Crisis questline is roughly 30-40 hours; the full game with all guilds (Dark Brotherhood, Thieves Guild, Fighters Guild, Mages Guild, Arena), Daedric quests, and side content runs 100-150 hours. The Shivering Isles expansion (included in the Remaster) adds ~30 more hours and is generally considered Oblivion's best content. There's no traditional New Game Plus, but the world stays fully accessible after the main credits — you can keep playing the same character indefinitely.

Source: Game Rant Hidden Quests