Question: Which is harder to exploit:
Password reset link with tokens/timestamps/code/ticket etc
Or, temporary password sent on user mail using which login can be done and password can be changed.

Any suggestions on how they can be exploited please?

Answer: 
They could be, phishing sites are set up to do exactly this.

On non-malicious sites, this would be generally be considered poor practice, but there is no reason why they couldn't, beyond user privacy regulations.
This would likely be recorded as an error on the website as it would return permission denied.
Many websites go through some kind of firewall or protection which might pick up failed attempted to try and block brute force log-in attempts or similar.

I would be pretty shocked to find that a (none compromised) website is storing passwords of failed log-in attempts, or any un-hashed/plaintext passwords at all.