Picture number one:
“1” is cable TV connection.
“2” Gravity water fill port. It is where you fill the fresh water holding tank.
“3” City water connection. Use a potable water hose with garden hose fitting to connect.
Picture number two:
Those are “low point” drains for letting water out of the fresh water system. Use then when sanitizing, winterizing or flushing the system.
Picture number three:
The tube is a storage place, possibly for a black tank drain hose. You don’t want waste contaminated things inside other storage spaces.
One of your stabilizing jacks is bent. You can get a replacement on https://www.etrailer.com/
Use their "chat" function to get advice if you need it.
You could probably remove it and bend it back. It would be good to weld reinforcements on where it bent.