Is the utterance of a supplication upon the tongue a guarantee of its acceptance or a sign of its acceptance, and does withholding the tongue from it indicate Allah's displeasure and non-acceptance?

There is no evidence that the utterance of supplication makes it answered or is a sign of its being answered, nor that withholding the tongue from supplication is considered a sign of Allah's wrath. Allah may divert a servant from supplicating against another out of mercy for him and for the other.