The rug with the rubber backing. If no, why not? I have been told not too but someone said it is no big deal.
I guess it would depend on the size of the rug, and the size of the tub in the washer. i wash all my rugs in my whirlpool duet. I have never had a problem. Sometimes, with front loaders, if the balance is not right, it will not spin out correctly, as it cannot balance the load. And like a top loader, you cannot just open up the lid and rebalance it manually. I always try to put something else in the washer with the rug or whatever I am washing to balance the load. But that does not always work out with, especially with pillows.
I think you probably could... Be sure it doesn't look ghetto though.. XD
Yes, I do it all the time with no problems, NEVER in the dryer though. I just hang it on the shower bar.
Yes you can. You may put some more kitchen rug also. Reason, Font loading machines has to distribute the load in spin. If not it will damage the Machine due to un balance. Rubber backing is not the problem. Generally there will be 3 ribs in the drum. The washing is happened when the cloth falls on the rib while on rotation. and in spin the weight is to be distributed in the space between the ribs.