Okie dokies, so this is a mini walkthrough that will hopefully help if you're stuck at any point :3 It will mention handy points to save at + how to get to all of the endings.

Part  1 - Welcome Home

This scene contains no choices, so if you're replaying from the beginning, you can use the skip text function to whizz through this section. To skip read text, press the skip button underneath the textbox, or press the spacebar. To skip unread text, open the config and turn unread text skipping on. (Using the skip text function in games made with Tyrano has been known to cause random crashes sometimes, but it doesn't seem to happen that often.)

Part 2 - The Basement

Just to be extra safe, you could make a save at the beginning of the scene where you wake up in the basement. You will soon encounter the first choice:

You're right. I'm an impostor. - This choice leads to one of the 3 main/'good' endings.  

You're wrong! I'm not an impostor!! - This choice continues on to the next section of the game.

Part 2.5 - The Basement - Waiting

You could make a save after choosing the 'You're wrong!' option. Another convenient place to save would be when your partner says the line 'Quit staring at me like that!'.

You will then encounter the first timed choice:

Lightbulb in the top left corner. - This leads to a small puzzle. Failing the puzzle will result in the same thing as if you'd let the choice timer run out. Entering the letters correctly will lead to one of the 3 main/'good' endings. (The answer is: IMPOSTOR!)

You're right. I'm an impostor. - This leads to the same one of 3 main/'good' endings as it would if you picked this choice the first time round.

Wait for timer to run out (timed choices are indicated by the heartbeat speeding up.) - This continues on to the next section of the game.

Part 3 - The Basement - Last Chance

You can save again after the timer has run out or after failing to input the correct word. Another convenient place to save is when your partner says the line 'No doubt, you despise me, but I don't care. You don't belong here! I'm just doing what's best for all of us.' Or, after pressing the button which says 'I need to tell you something.'

You will then encounter the final timed choice:

I know I'm real... but I'm not so sure I can say the same about you. - At first, this appears to be the only choice. It leads to one of the 2 bad ends.

I love you! - If you wait until the heartbeat timer almost runs out, this choice will appear 2 seconds before the timer (approx 20 secs) runs out. It leads to one of the 3 main/'good' ends.

Wait for timer to run out. - This leads to one of the 2 bad ends.

I think that's everything covered! If you have any questions, please feel free to contact me, and I'll do my best to help :3