Batteries will become unfit to use after they’ve been in the water. Usually however, a battery won’t leak inside the washing machine thanks to the safety valve - so chances of your textile being affected are minimal.
In appliances without a charging function, yes. In appliances that do have a charging function, be sure to check whether the function was specifically designed for Ni-MH. If not, it’s best not to use Ni-MH batteries.
Avoid contact with the substance at all times. Place the batteries into a plastic bag before recycling them. Clean out the battery holder with a dry cotton swab. In case of contact, wash your hands thoroughly with soap and water.
The memory effect is an occasional defect, which occurs in Ni-Cd and Ni-MH rechargeable batteries, where the maximum battery voltage decreases even though the original power of the battery remains the same.