哦, it has two meanings, one is positive respondse when somebody asking you a question or instructing you to do something, the other one is modal particle, express surprise or somthing, for example, you have been trying to figure out a difficult math problem for a long time, it seems like there is no solution, but all of sudden, a good idea come up in your mind and it's done, then you can say 哦, Basically, there is no difference among 哦，噢，喔,just used by different people at different age, the youth prefer to use 噢，喔 than 哦, I hope this could help you!

in a way ,”了“and”啦“ mean the same thing ,in english ,there will be words like "see" "saw"" seen"but in chinese ,you put "了""啦"after the verbs ，for example ,"i got my book back"="我把书要回来了/啦"，a difference is that "啦"sounds more entertaining。besides, "了"and”啦“use in certain sentences，such as "好了/啦"（okay，done），and ”啦“also is the word in ”lalala“，just a voice。”哦“”噢“”喔“aslo just like ”oh“in english 。this may not be very accurate ，i hope it will help you ：）。

The same. As a Chinese native speaker, I don't know the difference. Ignore it.

no strict rules about them