Splitting polygons into lines using QGIS?

Question

I have one shapelne that composed from many polygons. I wwant to create lines insides the polygons according to a given distance,

for example, this is the original plots-

and I want the lines to be like every 25 meters -sorry I draw it but it suppose to be symetricly-

I tried to create grids but because of the different of the plots it never sits perfectly, so even if I clip it I cant use it -

I also tried it with points and I rotated them but again , it doesn't match all the plots.

I am looking for tool that can create grid only inside the polygons.

my end goal is to be able to use this grid in order to locate points that have no coordinates data, based on distances.