‘Hello everyone’ in Japanese?

Hello everyone.
I usually use 'Konichiwa mina' but my boyfriend is more skilled in the language than I am and is unsure wether what I'm using is okay.
Which leads to my question: Is there more than one way to say'Hello everyone' in Japanese?

"Konichiwa mina'

If you want to be formal/speak in a polite speech, you must mean at least "Konnichiwa, minna" (please note how many "n" there are. "Ko-n-ni-chi-wa" is 5 syllables, and "mi-n-na" is 3 syllables.) But unless you are talking to a group of children, "minna" sounds a bit abrupt, ("mina" is just too blunt); you would want to say "mina-san" for "everyone."

If you want to say the same thing when, for example, you greet a class for the very first time and are introducing yourself, you could also say:
- Hajimemashite, mina-san. (Nice to see you/how do you do, everyone.)
But this is really for first time only.

minasan, konnichiwa.
is more common way to say informally.

Work/School:
If you're arriving at work/school for the first time that day, no matter what time it might be (even at night if you have the night shift!), you can say "mina-san, ohayo" or "mina-san, ohayao gozaimasu" (depending on the level of formality/familiarity) which is also saying "Hello everyone (I'm here!)"
I was confused when I first learned that since I learned it meant only "Good morning". Konnichiwa and Ohayo took some getting used to and I had a habit of catching myself in mid "konnichiwa" to make sure I wasn't saying the wrong thing in the wrong situation.

You can use "ohayo (gozaimasu)" when people arrive at work/school as well.
*I doubt that fact I lived in Kyushu when I learned/used this dismisses this as appropriate but if anyone can back me up, I'd appreciate it!

For first-time group meetings: It's acceptable to use "Mina-san, konnichiwa" or "Mina-san hajimemashite", like if you're starting out teaching a class of students, etc.

Informally: I sometimes used "Ya, minna" when I met up with my classmates after school for a drink.

Special Greeting: "Shokun, Osu!" I used with my judo and aikido club towards my juniors. They'd respond with a loud "osu" (‰Ÿ”E)
If you work for a crazy company like Hikari Tsushin, then "Osu mina-san!" is used all times of the day because it's an combination/abbreviation of "ohayo gozaimasu" and "onegai shimasu" (both start with "o" and end in "su")- probably not useful to you, but just thought you'd like to know! =)

So me using Konnichiwa Minna is acceptable if I use it to a bunch of my friends? But more polite to use minna-san in formal situations such as 'good morning class'

Thank you guys for your help :) I appreciate it.