Former employer dropping off poor reference of you to your prospective employer(s)

I am wondering if this case is prevalent in the IT industry.

The only reason why I left my former employer is because politics, despite my outstanding contributions. Since then, my lead really hated my guts and will do everything to throw me under the bus. Added note, upper management are very keen in keeping their trade secrets.

8 months later(btw i did get a job 2 weeks after I resigned), they still owe me my pro-rated 13 month pay and my BIR form. Again, another red flag(if you'd ask, I always do follow-ups every month and it seams like they don't care).

Recently, i am actively looking for another job opportunities. Since then, I now started to wonder if ever some of my prospect employers tried to call my former employer to get some reference, they might be dropping off poor reference about me to tarnish my reputation. The fact that I am technically well-versed with their product they might fear that I might breach their NON-COMPETE CLAUSE either by setting a competition against them or leaking their trade secrets.

I am starting to be skeptical about my job applications to prospect employers(IT industry) as I always mention that I had great contributions with this former employer and how great they are and how I look up to them.

To be honest, I really don't have any bad intentions towards them. I already let go of that a few months ago.

Is it good to ask my prospect employers to know if they've asked my former employer for reference and what has been told to them?

And what if my former employer really did dropped a poor reference of me to my prospect employers? What should I do if this happened?

I appreciate any legal advice.

you can ask but it some company does not divulge any result from their background investigation.