Can a star turn into a planet? I have read in a magazine that a star can actually form back to a planet... is it true?!
Does it mean all the planets in our galaxy can be revived back to what they were before?
No. This is not true.
A star is much larger than a planet.  A star has nuclear reactions in its core, that prevent it from collapsing under gravity.
A planet is much smaller. It is small enough for &quot;normal&quot; pressure to be strong enough to stop gravity from making it any smaller, and there are no thermonuclear reactions at its core.
A star cannot form back to a planet. A planet cannot be &quot;revived&quot; back to a star.
(There is one class of bodies that may be star-like when young and planet-like when older: &quot;Brown dwarfs&quot;.  These are objects with a mass of 15-75 times the mass of Jupiter. These can support deuterium fusion when young, but not hydrogen or even lithium fusion, when the deuterium is used up they don't have enough mass to collapse to a dense stellar remnant, and so become &quot;planet-like&quot;.  Really they are objects sui generis, neither stars nor planets. Non of the solar system planets are brown dwarfs, and you can't revive a brown dwarf.)