Can I use
"We make no prescriptions about ..."? This dictionary doesn't give any definition of the word
"prescription" apart from Medical or Legal jargon.
You're not using a good enough dictionary. Oxford dictionaries online gives:
So if that is what you mean by "prescription," your sentence is fine.
It is hard to say with such limited context ("We make no prescriptions about ..." what?) but the most general meaning is:
The action or an act of prescribing or setting down something beforehand, esp. as a rule, law, etc.; a thing which is prescribed or set down; written or explicit direction or injunction.
This would mean that in your sentence, "we are not setting any terms about (whatever) before (whatever)"