Rarely. It almost always follows the verb. Starting with 'Ju' is usually only done in the construction 'Ju förr, desto bättre' (The sooner, the better).
'Därför' is a conjunction meaning 'because of that.' 'Alltså' is a discourse marker meaning 'therefore' or 'in other words.'
Technically no, but Swedes sometimes do it for emphasis. However, as a learner, avoid it as it can be confusing or sound arrogant.
'Nog' is a particle used in speech to show a feeling, while 'troligtvis' is a formal adverb meaning 'statistically likely'.
It's rare and usually sounds redundant. Stick to one.
They help manage social harmony and shared knowledge.
