Beitza 26b

1- Hillel asked Rava regarding an object that was fit at the beginning of Shabbos, became unfit and then fit again. Is that object now muktzah?

Some background to understand the question:

In general, anything that is muktzah on Shabbos cannot be moved.

If it was muktzah at the beginning of Shabbos it remains muktzah for the entire Shabbos even if  it is not muktzah any longer. The beginning of Shabbos ‘locks in’ its status of muktzah.

Example: A burning candle at the beginning of Shabbos. It remains muktzah even after extinguished.

Now, if it becomes muktzah on Shabbos, it also cannot be moved.

Hillel’s question is if something becomes muktzah on Shabbos but then becomes non muktzah on Shabbos.

Do we say that once something becomes muktzah is remains in that state all Shabbos regardless of its change?

2- The example our Gemara uses is an edible fruit that is obviously not muktzah. But then it absorbed water and making it  inedible and therefore muktzah. A while later the fruit dries and is again edible.

Do we say that once an item becomes muktzah its status cannot be changed?

Rava responded that it is muktzah. Rava’s ruling is unsuccessfully challenged and according to a second version of this discussion Rava ruled that it is not muktzah.

That is indeed the Halachah.

3- We discussed the words of Rashi that the reason for muktzah is because one needs to prepare everything prior to Shabbos.

It follows,  that if one puts away something for a specific time, and by doing that it becomes muktzah, the item automatically become non-muktzah at the end of the time he designated. No special act or thought is needed to to revert it back to its non muktzah state.

Rashi bases this on the words of Reb Achai Goan.

See here.