In regards to Ein Bishul Achar Bishul … can a dry, solid, fully-cooked food every lose its cooked status. For example if I cook something and seal it for 10 years. After 10 years could I then take it out and warm it up on Shabbos (of course complying with all Halochos) utilising Ein Bishul Achar Bishul. If I had a cooked food in a bottle like instant coffee (which is cooked) could I still use it on Shabbos even though it was in my pantry for 10 years?
A solid dry food that was cooked stats cooked even if it is frozen for ten years. The cooking process has already taken place, and it is not going to turn raw even years later. There are poskim that say that if a cooked item was baked or roasted, that it is possible for it to lose its cooked status and it would not be permitted to recook it on Shabbos, however this is not the opinion of most poskim. For example, according to most poskim, if a cholent which was already cooked dried out, and is now considered roasted, it is permitted to add boiling water to it, even though it will now get recooked.
Kesiva vchasima tova
Pri Megadim O:CH 318 E:A 17, Biur Halacha 318 D:H Yesh, Iglei Tal Bishul 9 ftnt. 15,20 that this is the opinion of the majority of the poskim, Ketzos Hashulchan 124 ftnt. 54, Be’er Moshe 3-50, Shmiras Shabbos Khilchoso 1 ftnt. 48, PIskei Teshuvos 318-41.