You can’t tell it’s new just based off the picture. That could just be how the belt looks after “breaking in” for a while. It also looks similar to a belt I recently changed that had all these marks because I touched the belt with dirty hands and then the dirtiness spread around after being ran on the pulleys.

Lol you’re either a terrible mechanic or these people are just having car issues. Most likely it’s just normal car issues that happen with age there’s no real reason to this.

Yup you better be watching it constantly though. Every time you park check your oil and bring a 5gal jug of oil with you. Even if it doesn’t leak that much you could save if for next oil change