Of course it's OK. If you do so, we can figure out what do you want to say without difficulty. And every Japanese child who still has not been taught many kanji write article in this way. But if you did so, you cannot help being regarded as childish in this discriminative country. However, it's not your fault. It's a matter of course that foreign people don't know many kanji. I hope that you don't hesitate and carry out your way.

It's hard to understand if written only in hiragana and katakana. Here is an example I saw on the textbook in my childhood. はははははじょうぶだ。 →母は歯は丈夫だ。

You can, but it might be a bit confusing to read because there are so many homophones in Japanese! And also it's the standard to write using kanji.

I think it is difficult to read Japanese sentence without Kanji. because Japanese has many homonyms. So if you want to write in Japanese without Kanji, you should insert a space between each clause or words. For example, きょうは　てんきが　いいですね。 わたしは　だいがくに　かよっています。

I have learnt Japanese for 6 months. I find it really difficult. I had to study hard to pass N5 exams :)))).