If by "Can . . . ?" you mean to ask whether a lawfully
sentenced/incarcerated prisoner has an absolute "right" to do what you
ask, the answer (as should be obvious to you) is, No. Except,
depending on some facts/circumstances you don't make clear, for Q.3
re. which the answer is, Maybe.
Depending on the reasons for the incarceration, the needs and other
circumstances of the prisoner, the jurisdiction involved, etc., etc.,
some versions of what you ask are not uncommon as a matter of
practice. E.g., in the well-publicized case of a recently
(re)incarcerated well-known actor, that he will be receiving
substantial income from outside sources during his imprisonment
virtually requires that all the options to which you refer occur for
him, and they are.
But viz-a-viz your nos. 1 and 2, bear in mind, on the one hand, that
the sorts of things a lawfully criminally-sentenced/incarcerated
person may do with her/his funds and the sorts of things/services s/he
may buy and bring into the prison may be (actually, will be) strictly
regulated by the terms of the sentence or the prison authorities, or
both and, on the other hand, that it is common for folks who have
access to economic means (a minority of those in prison) to establish
commissary accounts which may be replenished by friends/family to
enable the purchase (from the jail authorities) of snacks, candy,
soap, other personal effects, etc.
In sum: The answer in any particular case will depend on the classic
five "W"s and the "H" (i.e., the proposed wHO, wHAT, wHEN, wHERE, wHY,
and hOW).
Michael Milken was even permitted to trade his own family's stock
positions while in federal prison. Normally you cannot continue to
operate a business while in jail, but there are a few exceptions.
And certainly, a person in jail can sign a power of attorney. Whether
or not a bank would accept such an instrument is another question. The
bank's rule of 'know your customer" is difficult to comply with if the
customer is in a cage.
McGyver
http://www.DavidPhipps.com