Hi .yes it is a ruin , however the walls and interior walls and staircases are intact and you can walk up the spiral staircase, i dont think there are any facilities for anyone to get up the staircase in a wheelchair etc etc .

2hrs would be enough

I think about £6/adult £20/family and free for disabled people and their carers. not sure about children and oaps, although I'm sure Google could tell you.

While officially dogs are welcome, my recollection is that this doesn't apply to all parts (for safety reasons). Your dog needs to be kept on a leash at all times.

Harlech train station is very close to the castle but you do have to walk up a very steep hill! Shouldn't take longer than 10-15 minutes and you can get a delicious ice cream at the top :)

My dog loved it only allowed in the grounds and not on the walls etc. The cafe has outdoor seats with lovely views. Lots of cadw castles allow dogs hope this helps. Enjoy x

Car park at front of castle charges £1 an hour (max stay 3 hours) - pay & display. It's not very big, so at peak times it may well be full.

There is a ramp to get into the castle but access when inside is very restrictive and personally I would not say wheelchair friendly

Dogs on leads are allowed, however probably wouldn't let them up the towers as the steps are very steep. However they would enjoy wandering around the grounds.

Yes as long as they are on a lead..