How many times can you apply for PIP?

I understand that if your PIP claim gets rejected, you can go to mandatory reconsideration. After that, it's tribunal.

If you don't want to go to tribunal, can you just reapply for PIP again, trying to take into account some of the feedback from the MR stage? Are here any limits/restrictions if there is no change in your condition, just you want to try to present your case differently?

A tribunal is often your best chance of getting the benefit. You can take somebody along for support if that would help you.