I can exactly say yes. we can write down all of sentences or words by Hiragana. so when you read comic book, you can read that even though you can not read Kanji, cuz all of comic have Hiragana printed beside them. for Katakana, we use that for words from overseas. so firstly I think you can recognize which letters are Katakana is enough to read.

Yes.

Hi ^_^ as a beginner ... first i learnt Hiragana ( i found it much easier ) and after i studied it all , i started with Katakana i think it depend on what do you find easier to learn and sooner or later you will study it all Good Luck :)