As far as I can tell, answers are as follows:

1. Allowed if vehicle has "Go to depot (stop)" order

<ST2> iI said it's ok to make a vehicle to START acceptance - that must be stopped after or make to the destination, to unload or transfer
<ST2> don't stopping vehicle leads you to breaking the "cheating" rule, and an admin can act as he want

2. Allowed if vehicle is stopped

<ST2> I fucking hate to repeat myself

3. Allowed but cargo can only be loaded from Pentwood West later.

<ST2> each vehicle on OpenTTD must have a purpose on the game: Load at one place and unload/transfer on another place
<ST2> as understandable, the unload must be on a place that accepts the cargo and transfers must have a use (on the moment, taken to other place - or to use later)