I've learned that the 1st to 10th day of the month is always read specially. However, when I converted these by using my computer typing "いちにち、ににち、さんにち、よんにち、ごにち、ろくにち、ななにち、はちにち、きゅうにち、じゅうにち、じゅうよんにち、にじゅうにち、にじゅうよんにち", these converted correctly. Especially, one-letter day expression can only be found when you convert correctly. For example, if you convert "よっか" or "よんにち", you can get a letter "㏣(IDEOGRAPHIC TELEGRAPH SYMBOL FOR DAY FOUR)". But, if you input "しにち" or "よにち", the letter is not shown within the candidates. I've learned that when you use generic counter for 1 to 10, you can use either "つ" or "こ". But, when you refer to over 10, You cannot use "つ", only "こ" can be used.
i) I wonder that the 1st to 10th, 14th, 20th and 24th day of the month also can be read as both "か" as "にち".
ii) And I wonder if I use "にち", the meaning is changed.