Is it obligatory to show gratitude for blessings? And is it permissible for a servant to thank Allah so that the blessings do not cease, or must the gratitude be for Allah and for nothing else?

Praise and gratitude to Allah are obligatory, as He commanded. The ruling regarding praise is that it is obligatory once in a lifetime with the intention of fulfilling the obligation; anything more than that is supererogatory. It appears that gratitude (shukr) is equivalent to praise (hamd) in its obligation. It is permissible to thank Allah to preserve His blessings and out of fear of their disappearance, for hoping for Allah’s mercy, coveting more of His blessings, and fearing His punishment do not contradict obedience to Him. Allah has described His prophets as those who hastened to good deeds and invoked Him with both hope and fear. The primary motive for gratitude must be the majesty and greatness of Allah, followed by the desire to preserve His blessings and seek an increase from them.