Yes!

A person's "brains" are never fully developed... with each new thing learned, it's said synaptic connection increase exponentially... which is why "AI" is a long way away... Anyway... if juvenile drops litter, as an example, they should be required to pick their own litter up, and then explain to people why it was they dropped the litter in the first place... chances are, a) they weren't aware of doing it (most of us are rarely aware of ALL our actions...), or b) they've never had it instilled into them by their lazy, lacklustre parents too preoccupied with their own lifestyles to remind little Johnny or Jane to be responsible for their own garbage, or c) they're arrogant little egos who think they've above such menial mindless tasks, and so, rather ironically, behave mindlessly...

I think it depends on a lot of things, but there needs to be more option for leniency where appropriate.

yes--option of rehabilitation since their brains do not finish developing until about age 25, especially related to risk-taking decisions

in some cases

Depends on the circumstances.

depends on the crime

depends on the crime

leaning yes

dependent on the circumstances and past offences